@mention should be a link
When we use @mention in a comment (to notify a user), it is rendered as mention. I would expect it to be a link to the user page.
I initially thought the current behavior was a bug, actually. Also, most systems I use that have this @mention system replace the login name by the full name of the user when rendered. @orenaud is replaced by Olivier Renaud which is a clickable link. To me both behaviors are fine, but the transformation to the full name reinforces the idea that the mention is correctly resolved.