It's a very hard forum to moderate regarding such abuse, since almost all discussions should be allowed within this forum.
This doesn't make any sense, you're saying the posts are valid but they're also abusive. Which is it? Here's a scenario:
General forum:
"What color are your eyes?"
"My eyes are blue"
"Mine too"
Site review forum:
"What do you think about my site?"
"I like the colors"
"Me too"
Ad revenue forum:
"Have you heard anything bad about these people?"
"No, only good"
"Me neither"
Of course, sometimes it's obvious who's posting just to inflate their post count while staying on topic, such as the third person here is. Sometimes it isn't. But, if it isn't obvious, then what's the problem? The second person here, each and every one of those posts could had been pulled straight out of his ass, but if they don't appear to be and seem, for all intensive purposes, to go along perfectly fine with the topic, what's the matter with them? Without knowing them all to be false, would you deem a post of a person who comments on the colors of a website or the good word of an advertiser as spam? Then why would you someone who responds to a question on their eye color? What's the difference? You say fluff posts are easier to spot on the other forums because of their narrower topics, I don't agree.
And there seems to be some contradiction, not from you specifically but from the general tone of the thread, as to what the post-count problem actually is. Post counts have only a few benefits, titles, avatars, custom titles, the top 10 list, that's about it. In one breath, post counts are touted for these. In the next, they're condemned for causing people to inflate their posts to try to attain them. Despite what many of you say, that they're just avatars and titles and of no real importance-- they are. If they meant nothing there would be no argument. In an idilic world, these benefits would come from years of thought-out, well-written, helpful posts, but let's not fool ourselves. With so few way to individualize yourself on a forum, trifles like avatars and titles do matter and people will strive by whatever means to get them. Cutting the count from one forum because of its broad topic wont stop this, not in the slightest. You don't stop a destructive force by removing one of it's eight means, you stop a destructive force by removing the desire to cause it. These "benefits" must be available to all or none and the post count must be abolished entirely. That would solve the problem.
But, in my opinion, it's a problem that doesn't need solving. I say, with more moderation, any of the blatant fluff posts on any of the forums could be spotted pretty quickly and taken care of, and those that aren't blatant... they're not hurting anyone. If by just reading a post you can't tell if it's abusive then chances are it isn't and even if it is, such as my "what color are your eyes/my eyes are blue" example, they're only abusive to the one who posted it, to everyone else it's perfectly acceptable. I've seen some beautiful, eloquent, thought-provoking posts here on the general forum in the past and I've seen incoherent, mindless, dribble posted on the free services and webspace forums. By just doing a silly little thing like counting or not counting the post toward the post count, you're elevating these later posts over the former, you're demeaning those because of the actions of spammers who aren't even going to be affected by the punishment. If you don't think this will demoralize those that spend virtually their entire visit on the general forum, you're sadly mistaken. The shear seeming-insignificance of post counts may mask it at first, but this change will take its effect on those that post here and almost nowhere else.