Hi Alice
If I get a chance to go through this in more detail I will, but for the moment here's a few hints.
First the usual disclaimer: I go through a lot of effort to pack these things into 140 characters, and often this means doing things in a very strange way just because it's a couple of characters shorter to write. (This one is very much one of those cases.) They're really not written to be understood. You're welcome to try and deconstruct them, and you might learn something useful from doing it - but that's not likely to include any kind of sensible coding style.
With that said, I can explain some useful points about these examples. In the first one I'm setting up 99 feedback loops using InFeedback, using bus numbers. In SuperCollider 3.4 and earlier, channels 0 to 15 are special (0 to 7 are outputs to the sound card and 8 to 15 are inputs), so the feedback busses are from 20 to 119, read by "Feeback.ar(20,99)". I don't want to use an Out UGen to write to these (it would cost around 8 or 9 characters) so instead I'm using the one added automatically by play{}, which starts writing from 0. So I let the function output an array which consists of the following:
* a stereo signal from Splay.ar, which occupies channels 0 and 1
* an array of 18 zeros, which occupies channels 2 to 19. This is to provide "padding" so that the next set of outputs will be in the correct channels.
* The signals for the feedback loop, given by (x-x.rotate/2), which occupies channels 20 to 119.
This (x-x.rotate/2) is what passes the feedback signal to the next one in the loop. The 'rotate' makes a version of the array where each element is shifted one index to the right (I think? Or maybe the left) and the final one is shifted back to the beginning. This is added to the original with a 180 degree phase shift (i.e. subtracted), so that each feedback channel gets a mixture between its own output and the output from one channel to the left.