Common reasons I downvote with no comment: I think the mistake is obvious to most readers (or already mentioned) and there's little to be gained from teaching the author. I think there's little insight and much noise - length, unpleasant style, politically disagreeable implications that would be tedious to pick apart (especially in tone rather than content). I judge that jerkishness is impairing comprehension; cutting out the courtesies and using strong words may be defensible, but using insults where explanations would do isn't.
On the "just a-holes" note (yes, I thought "Is this about me?"): It might be that your threshold for acceptable niceness is unusually high. We have traditions of bluntness and flaw-hunting (mostly from hackers, who correctly consider niceness noise when discussing bugs in X), so we ended up rather mean on average, and very tolerant of meanness. People who want LW to be nicer usually do it by being especially nice, not by especially punishing meanness. I notice you're on my list of people I should be exceptionally nice to, but not on my list of exceptionally nice people, which is a bad thing if you love Postel's law. (Which, by Postel's law, nobody but me has to.) The only LessWronger I think is an asshole is wedrifid, and I think this is one of his good traits.
We have traditions of bluntness and flaw-hunting (mostly from hackers, who correctly consider niceness noise when discussing bugs in X), so we ended up rather mean on average, and very tolerant of meanness.
I think there is a difference between choosing bluntness where niceness would tend to obscure the truth, and choosing between two forms of expression which are equally illuminating but not equally nice. I don't know about anyone else, but I'm using "a-hole" here to mean "One who routinely chooses the less nice variant in the latter situation."
(This is not a specific reference to you; your comment just happened to provide a good anchor for it.)
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A note for theists: you will find the Less Wrong community to be predominantly atheist, though not completely so, and most of us are genuinely respectful of religious people who keep the usual community norms. It's worth saying that we might think religion is off-topic in some places where you think it's on-topic, so be thoughtful about where and how you start explicitly talking about it; some of us are happy to talk about religion, some of us aren't interested. Bear in mind that many of us really, truly have given full consideration to theistic claims and found them to be false, so starting with the most common arguments is pretty likely just to annoy people. Anyhow, it's absolutely OK to mention that you're religious in your welcome post and to invite a discussion there.
A list of some posts that are pretty awesome
I recommend the major sequences to everybody, but I realize how daunting they look at first. So for purposes of immediate gratification, the following posts are particularly interesting/illuminating/provocative and don't require any previous reading:
More suggestions are welcome! Or just check out the top-rated posts from the history of Less Wrong. Most posts at +50 or more are well worth your time.
Welcome to Less Wrong, and we look forward to hearing from you throughout the site.
(Note from orthonormal: MBlume and other contributors wrote the original version of this welcome message, and I've stolen heavily from it.)