I can't see a problem with people talking about flight sims in an aviation related forum, although I would vote for a separate "Flight Sim" forum within PPRuNe.
The difference between PPRuNe and a forum like AVSim, is that AVSim is for general fans of flight sims.
A flight sim forum on PPRuNe would be for PILOTS who are fans of flight sims - there is a difference.
BTW: Does anyone have access to a decent free/shareware PA-28 Arrow II for FS2000?
Happy flying!