Tips for dealing with people with big egos:

• Don't insult anyone, ever. If Wagner posts, either say "Hmm, why do you believe Mendelssohn's music to be derivative?" or silently downvote, but don't call him an antisemitic piece of shit.
• Attributing negative motivations (disliking you, wanting to win a debate, being prejudiced) counts as an insult.
• Attributing any kind of motivation at all is pretty likely to count as an insult. You can ask about motivation, but only list positive or neutral ones or make it an open question.
• Likewise, you can ask why you were downvoted. This very often gets people to upvote you again if they were wrong to downvote you (and if not, you get the information you want). Any further implication that they were wrong is an insult.
• Stick closely to the question and do not involve the personalities of debaters.
• Exception to the above: it's okay to pass judgement on a personality trait if it's a compliment. If you can't always avoid insulting people, occasionally complimenting them can help.
• A lot of things are insults. You will slip up. This won't make people dislike you.
• If you know what a polite and friendly tone is, have one.
• If someone isn't polite and friendly, it means you need to be more polite and friendly.
• If they're being very rude and mean and it's getting annoying, you can gently mention it. Still make the rest of your post polite and friendly and about the question.
• If the "polite and about the question" part is empty, don't post.
• If you have insulted someone in a thread - either more than once, or once and people are still hostile despite you being extra nice afterwards - people will keep being hostile in the thread and you should probably walk away from it.
• If hostility in a thread is leaking into your mood, walk away from the whole site for a little while.
• When you post in another thread, people will not hold any grudges against you from previous threads. Sorry for your epic quest, but we don't have much against you right now.
• Apologies (rather than silence) are a good idea if you were clearly in the wrong and not overly tempted to add "but".

On politeness:

• Some politeness norms are stupid and harmful and wrong, like "You must not criticize even if explicitly asked to" or "Disagreement is impolite". Fortunately, we don't have these here.
• Some are good, like not insulting people. Insulting messages get across poorly. This happens even when people ignore the insult to answer the substance, because the message is overloaded.
• Some are mostly local communication protocols that help but can be costly to constrain your message around. It's okay to drop them if you can't bear the cost.
• Some are about fostering personal liking between people. They're worthwhile to people who want that and noise to people who don't.
• Taking pains to be polite is training wheels. People who are good with words can say precisely and concisely what they mean in a completely neutral tone. People who aren't are injecting lots of accidental interpersonal content, so we need to make it harmless explicitly.

People who are exempted:

• The aforementioned people, who will never accidentally insult anyone;
• People whose contribution is so incredibly awesome that it compensates for being insufferable; I know of a few but none on LessWrong;
• wedrifid, who is somehow capable of pleasant interaction while being a complete jerk.