Oh and going through posting history can be very misleading. Often the offending posts have been deleted so there is no trail for users to see, we can see it but to the casual observer it seems nothing is wrong.
To add to RainPilot's comment, there are also situations where there is a part of a post that is particularly inappropriate - personally insulting, offensive, whatever - but the post overall is related to the OP, and has useful information. In that case, we may go in and simply edit out the 'troublesome' part, after which a user will see the post, but not the problematic part, and may reasonably conclude that the post was 'OK'.
I has a very interesting discussion with a new sidemount student just the other evening. It was the first time I had met the gentleman, he was VERY, VERY well-prepared, and had obviously done a lot of background reading and viewing. I asked him what resources he had used. And, during our discussion I happened to mention, 'And, there is a lot of good information on ScubaBoard as well.' His reply was telling, 'Yeah, there's useful information, but I tend to avoid ScubaBoard because I have to wade through all the bickering, and drama, and insults just to get to anything good.' He made the comment not knowing I am a SB mod, so I took his response as 'real'. And, that is the unfortunate truth, for more than a few divers. They are simply put off by name-calling, blame-storming, agency-bashing, etc., etc. And, elect not to participate. Sometimes, we Mods may seem to be a little strident about enforcing some policies. But, we do it to make SB the kind of online presence that serves the larger body of users. At the same time, I know that some users really seem to enjoy reading sarcastic exchanges (to put it mildly). But, SB is NOT a cage fight, and we will continue to work to make sure that it doesn't become one.