[iosif]

I'm on the internet is not familiar enough, so let me admin put in place, if the idea is technically impracticable.
Its essence is to not let the unpleasant companions in their own theme.
Theme are always open one of uchastnkov forum. If he does not want to talk to some other participants - he puts them in a negative (of course, only for the topics of open them yourself). In other subjects one can not ban anyone, so there is no infringement of rights. We do not allow in your house of those who do not want to see.
Then people consciously (and inoffensive) would restrict the range of communication open to them themes.

Second option: turn off the unpleasant companions for your computer, just do not see their messages. Perhaps it is also possible?