In the account settings, I just noticed but there's options to tick for "friends" hinting that you could add friends on the forums?
As far as I can see this feature has been removed/un-ticked or I'm just blind but I did search my profile and some other peoples a few times for any buttons .
If this feature is available it would be cool to have to keep track of In-Game friends on the forums (for all-games).
Screenshot -