[jandrewrogers]

I have anecdotal insight. Many years ago I met with Jim Simons a few times. He had taken an interest in some of my theoretical computer science research (by referral, it was never published). I don't know any details of their strategies but one could infer it from their specific theoretical interests in those conversations.

My impression was that they were doing sophisticated sparse signal reconstruction and then applying some pattern induction algorithms against those signals. The former was, to the best I could discern, absolute state-of-the-art; the latter was merely competent (I've never talked to anyone that was exceptional at this bit). It has been a while but my impression was that a real strength was that this process was highly automated and general, so it could be thrown against almost arbitrary data sources. It is not difficult to imagine how one could build a sustainable and significant edge with this capability. I could be wrong but I don't think I am that far off. Very good math brains, even compared to many of their peers, based on my limited exposure.

I find their performance believable, given the above.

[deepnotderp]

You're not wrong, you're (almost) 100% correct, although they've certainly evolved their techniques since.

EDIT: I'm not saying that's everything, but automated signal extraction is a major part of their secret.