diff --git a/src/Lifecycle.js b/src/Lifecycle.js
index a3bec14492..bf7b25fd2b 100644
--- a/src/Lifecycle.js
+++ b/src/Lifecycle.js
@@ -237,7 +237,7 @@ function _handleRestoreFailure(e) {
             + ' This is a once off; sorry for the inconvenience.',
         );
 
-        _clearStorage();
+        _clearLocalStorage();
 
         return q.reject(new Error(
             _t('Unable to restore previous session') + ': ' + msg,
@@ -258,7 +258,7 @@ function _handleRestoreFailure(e) {
     return def.promise.then((success) => {
         if (success) {
             // user clicked continue.
-            _clearStorage();
+            _clearLocalStorage();
             return false;
         }
 
@@ -332,10 +332,6 @@ export function setLoggedIn(credentials) {
     }
 
     // stop any running clients before we create a new one with these new credentials
-    //
-    // XXX: why do we have any running clients here? Maybe on sign-in after
-    // initial use as a guest? but what about our persistent storage? we need to
-    // be careful not to leak e2e data created as one user into another session.
     stopMatrixClient();
 
     MatrixClientPeg.replaceUsingCreds(credentials);
@@ -406,19 +402,13 @@ export function startMatrixClient() {
  * a session has been logged out / ended.
  */
 export function onLoggedOut() {
-    stopMatrixClient(true);
+    _clearLocalStorage();
+    stopMatrixClient();
     dis.dispatch({action: 'on_logged_out'});
 }
 
-function _clearStorage() {
+function _clearLocalStorage() {
     Analytics.logout();
-
-    const cli = MatrixClientPeg.get();
-    if (cli) {
-        // TODO: *really* ought to wait for the promise to complete
-        cli.clearStores().done();
-    }
-
     if (!window.localStorage) {
         return;
     }
@@ -435,13 +425,9 @@ function _clearStorage() {
 }
 
 /**
- * Stop all the background processes related to the current client.
- *
- * Optionally clears persistent stores.
- *
- * @param {boolean} clearStores true to clear the persistent stores.
+ * Stop all the background processes related to the current client
  */
-export function stopMatrixClient(clearStores) {
+export function stopMatrixClient() {
     Notifier.stop();
     UserActivity.stop();
     Presence.stop();
@@ -450,13 +436,7 @@ export function stopMatrixClient(clearStores) {
     if (cli) {
         cli.stopClient();
         cli.removeAllListeners();
+        cli.store.deleteAllData();
+        MatrixClientPeg.unset();
     }
-
-    if (clearStores) {
-        // note that we have to do this *after* stopping the client, but
-        // *before* clearing the MatrixClientPeg.
-        _clearStorage();
-    }
-
-    MatrixClientPeg.unset();
 }
diff --git a/src/components/structures/MatrixChat.js b/src/components/structures/MatrixChat.js
index 0dedc02270..c4d3df03d3 100644
--- a/src/components/structures/MatrixChat.js
+++ b/src/components/structures/MatrixChat.js
@@ -292,7 +292,7 @@ module.exports = React.createClass({
     },
 
     componentWillUnmount: function() {
-        Lifecycle.stopMatrixClient(false);
+        Lifecycle.stopMatrixClient();
         dis.unregister(this.dispatcherRef);
         UDEHandler.stopListening();
         window.removeEventListener("focus", this.onFocus);
@@ -364,7 +364,7 @@ module.exports = React.createClass({
                 // is completed in another browser, we'll be 401ed for using
                 // a guest access token for a non-guest account.
                 // It will be restarted in onReturnToGuestClick
-                Lifecycle.stopMatrixClient(false);
+                Lifecycle.stopMatrixClient();
 
                 this.notifyNewScreen('register');
                 break;
@@ -507,7 +507,11 @@ module.exports = React.createClass({
                 this._onSetTheme(payload.value);
                 break;
             case 'on_logging_in':
-                this.setState({loggingIn: true});
+                // We are now logging in, so set the state to reflect that
+                // and also that we're not ready (we'll be marked as logged
+                // in once the login completes, then ready once the sync
+                // completes).
+                this.setState({loggingIn: true, ready: false});
                 break;
             case 'on_logged_in':
                 this._onLoggedIn(payload.teamToken);
diff --git a/src/components/structures/UserSettings.js b/src/components/structures/UserSettings.js
index 89debcb461..6cb262e79a 100644
--- a/src/components/structures/UserSettings.js
+++ b/src/components/structures/UserSettings.js
@@ -88,6 +88,10 @@ const SETTINGS_LABELS = [
         id: 'hideRedactions',
         label: 'Hide removed messages',
     },
+    {
+        id: 'disableMarkdown',
+        label: 'Disable markdown formatting',
+    },
 /*
     {
         id: 'useFixedWidthFont',
diff --git a/src/components/views/rooms/MessageComposerInputOld.js b/src/components/views/rooms/MessageComposerInputOld.js
index f6af20c03b..80fb51e6b5 100644
--- a/src/components/views/rooms/MessageComposerInputOld.js
+++ b/src/components/views/rooms/MessageComposerInputOld.js
@@ -29,7 +29,6 @@ var Markdown = require("../../../Markdown");
 
 var TYPING_USER_TIMEOUT = 10000;
 var TYPING_SERVER_TIMEOUT = 30000;
-var MARKDOWN_ENABLED = true;
 
 export function onSendMessageFailed(err, room) {
     // XXX: temporary logging to try to diagnose
@@ -77,7 +76,8 @@ export default React.createClass({
 
     componentWillMount: function() {
         this.oldScrollHeight = 0;
-        this.markdownEnabled = MARKDOWN_ENABLED;
+        this.markdownEnabled = !UserSettingsStore.getSyncedSetting('disableMarkdown', false);
+
         var self = this;
         this.sentHistory = {
             // The list of typed messages. Index 0 is more recent
diff --git a/src/components/views/rooms/RoomList.js b/src/components/views/rooms/RoomList.js
index f02f70b88b..3b43ea2b39 100644
--- a/src/components/views/rooms/RoomList.js
+++ b/src/components/views/rooms/RoomList.js
@@ -275,43 +275,6 @@ module.exports = React.createClass({
             }
         });
 
-        if (s.lists["im.vector.fake.direct"].length == 0 &&
-            MatrixClientPeg.get().getAccountData('m.direct') === undefined &&
-            !MatrixClientPeg.get().isGuest())
-        {
-            // scan through the 'recents' list for any rooms which look like DM rooms
-            // and make them DM rooms
-            const oldRecents = s.lists["im.vector.fake.recent"];
-            s.lists["im.vector.fake.recent"] = [];
-
-            for (const room of oldRecents) {
-                const me = room.getMember(MatrixClientPeg.get().credentials.userId);
-
-                if (me && Rooms.looksLikeDirectMessageRoom(room, me)) {
-                    s.lists["im.vector.fake.direct"].push(room);
-                } else {
-                    s.lists["im.vector.fake.recent"].push(room);
-                }
-            }
-
-            // save these new guessed DM rooms into the account data
-            const newMDirectEvent = {};
-            for (const room of s.lists["im.vector.fake.direct"]) {
-                const me = room.getMember(MatrixClientPeg.get().credentials.userId);
-                const otherPerson = Rooms.getOnlyOtherMember(room, me);
-                if (!otherPerson) continue;
-
-                const roomList = newMDirectEvent[otherPerson.userId] || [];
-                roomList.push(room.roomId);
-                newMDirectEvent[otherPerson.userId] = roomList;
-            }
-
-            // if this fails, fine, we'll just do the same thing next time we get the room lists
-            MatrixClientPeg.get().setAccountData('m.direct', newMDirectEvent).done();
-        }
-
-        //console.log("calculated new roomLists; im.vector.fake.recent = " + s.lists["im.vector.fake.recent"]);
-
         // we actually apply the sorting to this when receiving the prop in RoomSubLists.
 
         return s;
diff --git a/src/i18n/strings/en_EN.json b/src/i18n/strings/en_EN.json
index 2bef4b8901..6a7c510544 100644
--- a/src/i18n/strings/en_EN.json
+++ b/src/i18n/strings/en_EN.json
@@ -241,6 +241,7 @@
   "Direct chats": "Direct chats",
   "disabled": "disabled",
   "Disable inline URL previews by default": "Disable inline URL previews by default",
+  "Disable markdown formatting": "Disable markdown formatting",
   "Disinvite": "Disinvite",
   "Display name": "Display name",
   "Displays action": "Displays action",
diff --git a/src/languageHandler.js b/src/languageHandler.js
index 798798b6e5..68e8ca6172 100644
--- a/src/languageHandler.js
+++ b/src/languageHandler.js
@@ -35,6 +35,25 @@ counterpart.setFallbackLocale('en');
 // just import counterpart and use it directly, we end up using a different
 // instance.
 export function _t(...args) {
+    // Horrible hack to avoid https://github.com/vector-im/riot-web/issues/4191
+    // The interpolation library that counterpart uses does not support undefined/null
+    // values and instead will throw an error. This is a problem since everywhere else
+    // in JS land passing undefined/null will simply stringify instead, and when converting
+    // valid ES6 template strings to i18n strings it's extremely easy to pass undefined/null
+    // if there are no existing null guards. To avoid this making the app completely inoperable,
+    // we'll check all the values for undefined/null and stringify them here.
+    if (args[1] && typeof args[1] === 'object') {
+        Object.keys(args[1]).forEach((k) => {
+            if (args[1][k] === undefined) {
+                console.warn("_t called with undefined interpolation name: " + k);
+                args[1][k] = 'undefined';
+            }
+            if (args[1][k] === null) {
+                console.warn("_t called with null interpolation name: " + k);
+                args[1][k] = 'null';
+            }
+        });
+    }
     return counterpart.translate(...args);
 }