Time for some input from me. First some background; I am a member of a few other forums and for my sins I am also a moderator on one of them. The topic is completely different but lots of the issues highlighted here are the same.
It will always be impossible to please everyone. As a forum grows, and this one is growing at a rapid rate, the place changes. When it's quite small lots of people personally know many other members and thus a lot of the threads appear like conversations that might be had face to face. When you have had lots of new members, particularly youngsters who aren't really clued up on how a forum should work (Not trying to over generalise, so please don't take offence), conversations take on a different perspective. Members are seen as faceless usernames and misunderstandings can often escallate quickly. The fact that some forums are completely unregulated doesn't help because people think they can act in the same way on any forum.
This forum is a very well run forum, imo. From what I've seen the moderation is firm but fair. Hell, I even fell foul of it myself shortly after I'd joined because a post I made broke a rule that I'd never considered would be a problem. I was peeved at the time, even thought about leaving, but it's all forgotten now.
As places evolve, sometimes they alienate some of the members. This can be difficult, especially if it's someone well liked or long standing, but in most cases it's important not to try too hard to react. If someone doesn't like a place (be it a pub, club or online forum) then it's natural to drift away and find other things to do. There's one particular forum where I was very active for about 2 years, then my interests changed and the place no longer seemed relevant to my life. Places like RailUK are great because there is a very strong community. I've got quite a few real-life friends on here now, but if I was ever to lose interest in railways it's unlikely that I'd stay around.
One of the great things about RailUK is that they are evolving and the staff actively seek views of the members to help them follow the right path. As the membership grows it becomes increasingly difficult to please everyone, and people who find that the place isn't quite what they thought it was will leave. With the mechanisms to discuss/liaise with the forum staff (report, message to the staff, questionnaires, etc) anyone who either won't use them or doesn't agree with the outcome is probably not worth having as a member.
I've waffled more than I intended, but the crux of my view is that there is very little wrong here compared to most other forums.
Finally, I'm all too aware that I do sometimes post in an inappropriate way. Although I try to read every post back before hitting submit, I'm aware that I do come across wrongly sometimes. If I've upset anyone along the way then I'm sorry. If you tell me then I can improve, but if you let me carry on regardless then how can I know. Sometimes all it needs is a quiet PM to explain why someone is upsetting others and they will try to change.