fixes flickers in avatar mention dropdown

app/assets/stylesheets/framework/animations.scss

@@ -71,6 +71,27 @@
   transition: $unfoldedTransitions;
 }
 
+@mixin disableAllAnimation {
+  /*CSS transitions*/
+  -o-transition-property: none !important;
+  -moz-transition-property: none !important;
+  -ms-transition-property: none !important;
+  -webkit-transition-property: none !important;
+  transition-property: none !important;
+  /*CSS transforms*/
+  -o-transform: none !important;
+  -moz-transform: none !important;
+  -ms-transform: none !important;
+  -webkit-transform: none !important;
+  transform: none !important;
+  /*CSS animations*/
+  -webkit-animation: none !important;
+  -moz-animation: none !important;
+  -o-animation: none !important;
+  -ms-animation: none !important;
+  animation: none !important;
+}
+
 @function unfoldTransition ($transition) {
   // Default values
   $property: all;

app/assets/stylesheets/framework/markdown_area.scss

@@ -159,6 +159,7 @@
   .cur {
     .avatar {
       border: 1px solid $white-light;
+      @include disableAllAnimation;
     }
   }
 }