diff --git a/src/autocomplete/Autocompleter.js b/src/autocomplete/Autocompleter.js
index e47c5dd59c..6fadf53a61 100644
--- a/src/autocomplete/Autocompleter.js
+++ b/src/autocomplete/Autocompleter.js
@@ -34,6 +34,12 @@ export type Completion = {
     component: ?Component,
     range: SelectionRange,
     command: ?string,
+    // An entity applied during the replacement (using draftjs@0.8.1 Entity.create)
+    entity: ? {
+        type: string,
+        mutability: string,
+        data: ?Object,
+    },
 };
 
 const PROVIDERS = [
diff --git a/src/autocomplete/RoomProvider.js b/src/autocomplete/RoomProvider.js
index bf8495a90e..ed737a7d96 100644
--- a/src/autocomplete/RoomProvider.js
+++ b/src/autocomplete/RoomProvider.js
@@ -52,9 +52,16 @@ export default class RoomProvider extends AutocompleteProvider {
                 };
             }));
             completions = this.matcher.match(command[0]).map(room => {
-                let displayAlias = getDisplayAliasForRoom(room.room) || room.roomId;
+                const displayAlias = getDisplayAliasForRoom(room.room) || room.roomId;
                 return {
-                    completion: displayAlias + ' ',
+                    completion: displayAlias,
+                    entity: {
+                        type: 'LINK',
+                        mutability: 'IMMUTABLE',
+                        data: {
+                            url: 'https://matrix.to/#/' + displayAlias,
+                        },
+                    },
                     component: (
                         <PillCompletion initialComponent={<RoomAvatar width={24} height={24} room={room.room} />} title={room.name} description={displayAlias} />
                     ),
diff --git a/src/autocomplete/UserProvider.js b/src/autocomplete/UserProvider.js
index f052716b4b..c17d56312b 100644
--- a/src/autocomplete/UserProvider.js
+++ b/src/autocomplete/UserProvider.js
@@ -51,16 +51,17 @@ export default class UserProvider extends AutocompleteProvider {
         let completions = [];
         let {command, range} = this.getCurrentCommand(query, selection, force);
         if (command) {
-            completions = this.matcher.match(command[0]).slice(0, 4).map((user) => {
-                let displayName = (user.name || user.userId || '').replace(' (IRC)', ''); // FIXME when groups are done
-                let completion = displayName;
-                if (range.start === 0) {
-                    completion += ': ';
-                } else {
-                    completion += ' ';
-                }
+            completions = this.matcher.match(command[0]).map((user) => {
+                const displayName = (user.name || user.userId || '').replace(' (IRC)', ''); // FIXME when groups are done
                 return {
-                    completion,
+                    completion: displayName,
+                    entity: {
+                        type: 'LINK',
+                        mutability: 'IMMUTABLE',
+                        data: {
+                            url: 'https://matrix.to/#/' + user.userId,
+                        },
+                    },
                     component: (
                         <PillCompletion
                             initialComponent={<MemberAvatar member={user} width={24} height={24}/>}
diff --git a/src/components/views/rooms/MessageComposerInput.js b/src/components/views/rooms/MessageComposerInput.js
index 2f0901018d..a2bbe7a812 100644
--- a/src/components/views/rooms/MessageComposerInput.js
+++ b/src/components/views/rooms/MessageComposerInput.js
@@ -190,9 +190,16 @@ export default class MessageComposerInput extends React.Component {
                 const MemberAvatar = sdk.getComponent('avatars.MemberAvatar');
                 const RoomAvatar = sdk.getComponent('avatars.RoomAvatar');
                 const {url} = Entity.get(props.entityKey).getData();
-                const matrixToMatch = REGEX_MATRIXTO.exec(url);
-                const isUserPill = matrixToMatch[2] === '@';
-                const isRoomPill = matrixToMatch[2] === '#' || matrixToMatch[2] === '!';
+
+                // Default to the empty array if no match for simplicity
+                // resource and prefix will be undefined instead of throwing
+                const matrixToMatch = REGEX_MATRIXTO.exec(url) || [];
+
+                const resource = matrixToMatch[1]; // The room/user ID
+                const prefix = matrixToMatch[2]; // The first character of prefix
+
+                const isUserPill = prefix === '@';
+                const isRoomPill = prefix === '#' || prefix === '!';
 
                 const classes = classNames({
                     "mx_UserPill": isUserPill,
@@ -203,14 +210,14 @@ export default class MessageComposerInput extends React.Component {
                 if (isUserPill) {
                     // If this user is not a member of this room, default to the empty
                     // member. This could be improved by doing an async profile lookup.
-                    const member = this.props.room.getMember(matrixToMatch[1]) ||
-                        new RoomMember(null, matrixToMatch[1]);
+                    const member = this.props.room.getMember(resource) ||
+                        new RoomMember(null, resource);
                     avatar = member ? <MemberAvatar member={member} width={16} height={16}/> : null;
                 } else if (isRoomPill) {
-                    const room = matrixToMatch[2] === '#' ?
+                    const room = prefix === '#' ?
                         MatrixClientPeg.get().getRooms().find((r) => {
-                            return r.getCanonicalAlias() === matrixToMatch[1];
-                        }) : MatrixClientPeg.get().getRoom(matrixToMatch[1]);
+                            return r.getCanonicalAlias() === resource;
+                        }) : MatrixClientPeg.get().getRoom(resource);
                     avatar = room ? <RoomAvatar room={room} width={16} height={16}/> : null;
                 }
 
@@ -910,12 +917,24 @@ export default class MessageComposerInput extends React.Component {
             return false;
         }
 
-        const {range = {}, completion = ''} = displayedCompletion;
+        const {range = {}, completion = '', entity = null} = displayedCompletion;
+        let entityKey;
+        if (entity) {
+            entityKey = Entity.create(
+              entity.type,
+              entity.mutability,
+              entity.data,
+            );
+        }
 
         const contentState = Modifier.replaceText(
             activeEditorState.getCurrentContent(),
-            RichText.textOffsetsToSelectionState(range, activeEditorState.getCurrentContent().getBlocksAsArray()),
+            RichText.textOffsetsToSelectionState(
+                range, activeEditorState.getCurrentContent().getBlocksAsArray(),
+            ),
             completion,
+            null,
+            entityKey,
         );
 
         let editorState = EditorState.push(activeEditorState, contentState, 'insert-characters');