CommenterUsername
This template tag returns the username of the current commenter in context. If no name exists, then it returns an empty string.
Example:
<mt:Entries>
<h1><$mt:EntryTitle$></h1>
<mt:Comments>
<a name="comment-<$mt:CommentID$>"></a>
<p><$mt:CommentBody$></p>
<cite><a href="/profiles/<$mt:CommenterID$>"><$mt:CommenterUsername$></a></cite>
</mt:Comments>
</mt:Entries>