I don't have long to type this post, but I will address your points in the same order you did.
1) If you don't like /personal/, don't go there. Not every single board on this site caters to everyone's interests or likes. I'm sure there are people here who think /love/ is just for people who can't get laid, or that /dqn/ is for retards. So they don't go there. Easy solution.
2) Of course there's an anti-tripcode sentiment on a board that is based on anonymous discussion. The vast majority of 4-ch users (and, to the best of my knowledge, 2ch users) agree that in MOST situations, an anonymous discussion works best when everyone is anonymous, and that anyone who tries to not be anonymous (ie by using a name and tripcode) is doing it to stand out, which is looked down upon.
3) Just as you can't explain this point, I don't really have an answer or explanation, except that I haven't noticed it. Sure, a lot of people here are the hikki type, or otherwise socially awkward, but a lot aren't, as well. /shrug
4) The idea of this board came from a Japanese one, so of course there's going to be a large community of people here that are interested in Japanese culture.