I'm sure someone mentioned this but is there any chance of a facility for private messages? (this could be limited to a 5 message limit or the like for space considerations).
On forums where I have moderated those have been very useful - they can act as a sort of invisible social glue. It allows people to say "don't you think you are being a little harsh there...." without a thread being dragged down into "no he wasn't being harsh and here are the 50,000 previous threads that prove my point". It allows people to say "hey I realise that my words could come across a little harsh and I'm sorry about that" - something that people struggle with in an open forum for a number of reasons.