poster_expansion will only slide down now.

app/assets/javascripts/discourse/views/poster_expansion_view.js

@@ -15,7 +15,7 @@ Discourse.PosterExpansionView = Discourse.View.extend({
   // Position the expansion when the post changes
   _visibleChanged: function() {
     var post = this.get('controller.model'),
-        self = this;
+        div = this.$();
 
     Em.run.schedule('afterRender', function() {
       if (post) {
@@ -25,8 +25,14 @@ Discourse.PosterExpansionView = Discourse.View.extend({
 
         if (position) {
           position.left += $avatar.width() + 5;
-          self.$().css(position);
+          div.css(position);
         }
+
+        var maxWidth = div.width();
+        if (maxWidth < 250) {
+          maxWidth = 250;
+        }
+        div.css({ maxWidth: maxWidth });
       }
     });
 
@@ -52,4 +58,4 @@ Discourse.PosterExpansionView = Discourse.View.extend({
     $('html').off(clickOutsideEventName);
   }
 
-});
+});

app/assets/stylesheets/desktop/poster_expansion.scss

@@ -11,9 +11,10 @@
   margin-top: -2px;
   background-color: $primary_background_color;
   padding: 12px 12px 5px 12px;
-  max-width: 350px;
 
   h1 {
+    display: inline-block;
+    min-width: 120px;
     font-size: 30px;
     line-height: 33px;
     margin-bottom: 8px;