Set textarea resize:vertical by default.

app/assets/stylesheets/generic/forms.scss

+textarea {
+  resize: vertical;
+}
+
 input[type='search'].search-text-input {
   background-image: image-url("icon-search.png");
   background-repeat: no-repeat;

app/assets/stylesheets/sections/commits.scss

@@ -244,7 +244,6 @@ li.commit {
     font-family: inherit;
     padding-left: $left;
     position: relative;
-    resize: vertical;
     z-index: 2;
   }
 }