Finished up an argument with a materialist a couple of days ago. A few things I've learned.
* If a person uses a lot of :) symbols when they argue, and makes plenty of indirect insults rather than direct ones, a surprising number of theists will go on about how nice and civil and polite and smart the person is. Apparently the internet has reached a point where you can be a smug, inept, insulting jackass and so long as you're subtle people will praise you like crazy.
* Self-contradiction is a hard concept for people to grasp. Argue that a given person X is making an argument which is self-contradictory or incoherent - say, that they say A, and they also say B, and A and B are incompatible - don't be surprised if they respond to you, "Well, he couldn't be saying A! Because look, he says B! And B isn't compatible with A!" That the point is that A and B are incompatible, and that it's even possible for a person to make a contradictory or incoherent argument, seems to not even register for some people. Unless, of course, they disagree with the person in question.
* There are materialists who think saying the words 'emergence' or 'recursion' is sufficient to completely defend materialism, particularly with regards to the mind. Really, all they have to do is say 'the self emerges' or 'experiences emerge' or 'consciousness is recursion' - no more explanation than that - and they think they're done. Point out that some types of emergence are in principle impossible, unless emergence is brute, and they seem to not even notice.
Just proving more and more that arguing on the internet is (surprise) pretty hopeless.