We were very impressed by the feature of "automagic issue linking" where using a known issue-key in any form of comment would result in a link pointing that very issue.

I would like to request a similar feature of "automagic user linking and mailing". One could create an issue, or comment on one, and use a known username. JIRA then not only adds a link to that user (not so useful) but also generates and sends an e-mail to that user notifying of this issue's change, possibly inviting him/her to watch it.

Ex:
Comment "This is something I need j.doe for." would result in the actual comment "This is something that I need John Doe for." and an e-mail to j.doe@blah.com with a notification.