As also mentioned in post 15 of this thread (http://kdenlive.org/forum/please-remove-spammer-kelisi007-and-other-spam... )
(and sorry for cross posting which is of course also a form of spam :) )
I have also reported many spammers over the past months.
Most forum software packages have an option that the first post from a new user goes into a moderation queue. Once it is approved, that user then has normal posting rights.
Of course this makes it less user friendly for first time users as it will take (a little) longer before their first post shows up in the forum but it keeps spam almost 100% under control.
I know it from many forums I attend and have attended and it works fine.