Mentions should automatically add a mentioned user as a watcher to the issue.

Mentions would rock (moreso than it does already) if I, as a mentioned user, am automatically added as a watcher to an issue I'm mentioned in. I find that my normal workflow when I'm mentioned is to have a back and forth within the issue itself via comments, and unless I manually add myself as a watcher in order to receive notifications I can sometimes miss out on further questions or comments that are relevant to me.

Ideally watching would be automatic, and the ability to unwatch be provided in email notifications I receive from the system.