It’s easy to sit in the safety of one wine forum, and criticise others. I remember one forum owner in the past be very firm that he saw no value in his forumites getting into a flame war with other forum (and at the time the other forum in the cross-hairs was this one). I agree with him.
I currently post on 2 wine forums and a travel forum. That’s enough considering the length of my waffle.
In terms of other forums and why to post there, firstly the active forums:
Auswine - Generally very polite & supportive, a great place to get a feel for the always dynamic Aussie wine scene, but also now increasingly interesting for Nebbiolo / Italian wines and Burgundy, plus growing interest elsewhere. Very hands-off moderation - there is no need given the positive attitudes.
Wine Berserkers - Very active, and has been at the heart of unearthing some major wine stories (Rudy, Premier Cru, Maison Ilan). A definite edge to it at times, and that can occasionally boil over from feisty to something worse, but it has a reputation that inaccurately focuses on the train wrecks and not the other 99% of threads. There is much more considered thought than it is given credit for. Also strong away from wine (beer, travel,etc.).
SlowEurope (Travel forum). Re-born after the original SlowTrav website was bought out, left to rot and then closed. A focus on ‘Slow’ travel, the opposite of those glossy brochures that claim you can ‘see Italy’ in a week. Not everyone travels ‘slow’, and a credit to the forumites that those seeking whistlestop tours are given helpful advice. A very friendly site with active moderation. Much more clued-up posters than (say) Trip Advisor, but way less traffic than it. Go here first, but then if you can’t find anything, try Trip Advisor. Italy a particular focus, but UK, France and the rest of Europe also get a good look-in. The best site I’m aware of for asking ‘I think I want to go to X, but need help in working out exactly where to go’.
Wine Pages. Again very friendly and actively moderated. Broad cross-section of interests, maybe not quite as old-school as it was, but still a major part. Active London-based offline sub-forum, and have been welcoming to visitors from outside the UK / the forum.
Wine Lovers Discussion Forum. One of the oldest online wine forums. Very friendly and with food an active part of the discussion. Much less posting than here, though some familiar names post across the two sites. Also hosts an Israeli wine forum, which was set up by (Daniel) Rogov. Despite having no experience of Israeli wines, I used to enjoy posting there when he was still alive, as for me he was as good as anyone at the (very difficult) art of moderation, using discussion to defuse and offer alternative opinions without ever resorting to criticism or trenchant rhetoric. That sub-forum still persists, but I believe it’s now more about the wines than the wider ranging topics that would get mulled over.