Comment hot fix

Closes #2929 
Refs #2894 
Adds back the ability to reply to and edit comments on a self-hosted site. 
Adds new functionality for displaying an avatar image when `avatarImageForDisplay` is nil 
Fixes an issue with how the return value of the call to wp.editComment was used. 
Is there a reason why this isn't using `self.commentService`. I'm not a big fan of caching service instances, but the rest of the class seems to be doing that.