Fix review problems

- removed superfluous position and classes
- fixed compact view
- fixed event list summary avatar and text overlap
- fixed a problem where the mention list refuses to load.

res/css/views/rooms/_GroupLayout.scss

@@ -47,6 +47,86 @@ $left-gutter: 65px;
     }
 
     .mx_EventTile_info .mx_EventTile_line {
-        padding-left: 83px;
+        padding-left: calc($left-gutter + 18px);
     }
 }
+
+/* Compact layout overrides */
+
+.mx_MatrixChat_useCompactLayout {
+    .mx_EventTile {
+        padding-top: 4px;
+    }
+
+    .mx_EventTile.mx_EventTile_info {
+        // same as the padding for non-compact .mx_EventTile.mx_EventTile_info
+        padding-top: 0px;
+        font-size: $font-13px;
+        .mx_EventTile_line, .mx_EventTile_reply {
+            line-height: $font-20px;
+        }
+        .mx_EventTile_avatar {
+            top: 4px;
+        }
+    }
+
+    .mx_EventTile .mx_SenderProfile {
+        font-size: $font-13px;
+    }
+
+    .mx_EventTile.mx_EventTile_emote {
+        // add a bit more space for emotes so that avatars don't collide
+        padding-top: 8px;
+        .mx_EventTile_avatar {
+            top: 2px;
+        }
+        .mx_EventTile_line, .mx_EventTile_reply {
+            padding-top: 0px;
+            padding-bottom: 1px;
+        }
+    }
+
+    .mx_EventTile.mx_EventTile_emote.mx_EventTile_continuation {
+        padding-top: 0;
+        .mx_EventTile_line, .mx_EventTile_reply {
+            padding-top: 0px;
+            padding-bottom: 0px;
+        }
+    }
+
+    .mx_EventTile_line, .mx_EventTile_reply {
+        padding-top: 0px;
+        padding-bottom: 0px;
+    }
+
+    .mx_EventTile_avatar {
+        top: 2px;
+    }
+
+    .mx_EventTile_e2eIcon {
+        top: 3px;
+    }
+
+    .mx_EventTile_readAvatars {
+        top: 27px;
+    }
+
+    .mx_EventTile_continuation .mx_EventTile_readAvatars,
+    .mx_EventTile_emote .mx_EventTile_readAvatars {
+        top: 5px;
+    }
+
+    .mx_EventTile_info .mx_EventTile_readAvatars {
+        top: 4px;
+    }
+
+    .mx_RoomView_MessageList h2 {
+        margin-top: 6px;
+    }
+
+    .mx_EventTile_content .markdown-body {
+        p, ul, ol, dl, blockquote, pre, table {
+            margin-bottom: 4px; // 1/4 of the non-compact margin-bottom
+        }
+    }
+}