Right, I have now caught up (by skimming, so forgive me if I miss out a few points).
I think whoever made the point about pile-ins seeming to be the same people all the time being due to threads appearing in active is true.
I have much more than half the board hidden. So I suspect my active conversation threads has very few topics, so I tend to notice and post on those topics much more than others.
People who haven't sorted out how to hide topics won't realise that, so their AC will be full of antenatal and postnatal and prams and crap 
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I suspect that lots of oldies also have the same topics hidden as I have, so we all tend to be more active on the topics that are left. Added to which some of us are here a lot due to real life going that way.
I have never seen a newbie told not to post - but have suggested to a few not to post their first posts in aibu. In fact I positively encourage newbies, I love 'em and encourage them to post lots and lots.
I seldom call troll, but I have a very short threads I'm watching list because almost ever thread I think is a troll is a troll and disappears. But I still give advice to trolls (as well as reporting), like the debt one this morning - very odd, but not worth taking the mickey. Obviously if people had started offering money (they may have, I went out), I would have shouted more loudly.
LDNMummy - the traveller you are talking about was Beesimo, and I wouldn't waste sympathy on her as she (a) wasn't a traveller and (b) gave much more than she got. If you are talking about sm bullying you, that also has more to it than meets the eye - you may have felt bullied, but I doubt very much sm even noticed who you were. To her, it is all definitely words on a screen. And finally, most people who are called trolls sadly are. And trolls do a lot of harm. So while I don't call troll on thread (except in extreme circumstances), I can understand why people who have been duped in the past and recognise the situation, poster or post, do.