When username contains <, users profile page displays Incorrectly.

Pre-conditions: register and activate user <yak.

Steps to reproduce:
1. Login jcommune with user which have permission to create posts.
2. Go to any topic and click "answer".
3. Enter [user]<yak[/user] in the text field and click "answer"
4. click on the link to <yak profile.

AR: Users profile page displays incorrectly: completely gray, without borders, with incorrect text on the Tab (see attachment).
ER: Users profile page displays correctly: white area with text field, text "user <yak" on the Tab.