I've seen a few new people with this problem, but I see many many more who don't have it. Plenty of new bods settle in and become part of the fabric with no trouble at all. All it takes is a little finding out what kind of thing goes down well, and what is frowned upon.
When entering into a new social group of any sort, most people take some time to acclimatise, to find out what the tone of that group is. Same with internet forums. You wouldn't like it if someone came all up in your face, talking about things you weren't interested in, in a manner you found irritating. You'd be even more annoyed if they then demanded acceptance from you and your friends without taking the time to find out anything about you. It's made worse online because you don't have contact with that person, you have nothing to judge them on but their words (hence why we value good spelling and syntax, it hopefully reduces any ambiguity).
Bit of an exaggerated example, but hopefully you get the point. You can see by reading a few of the posts around here what kind of place it is and what kind of posting goes down well. Tolerance goes both ways. This site gives plenty, and really doesn't ask much in return. Further, given that this site has to deal with cheats, liars and the like in the competitions, it's understandable that people's moron radars are pretty active. Show you've got something to contribute and you won't fall foul of them.
Addressing the specific points: KS8, a lot of what appears scolding is down to sense of humour (my recent picking up on typos, for instance). We do it to each other too (at least I do, and I definitely expect it in return!). The rest is generally only when someone's been asked nicely not to do something first. Also, you've got to remember we've had some serious idiots here before. Cake: don't worry about it, just think about what you're posting and I'm sure it'll be cool.
Damnit, I hate being serious about stuff, must do something about it. Be prepared for a backlash of sarcasm and toilet humour >_>