There is currently no way to take away someone's ability to leave profile comments for other users without banning or suspending their account. I expected that the "Prevent Status Updates" setting would do this, as status updates and profile comments were merged in IP.Board 3.2, but it doesn't.

This would be a useful addition to IPB's arsenal of moderation tools, as we occasionally run into users who leave abusive profile comments but don't quite deserve a full ban.

Definitely a good idea.