when someone recasts a post, where does it go? i don't see any recasts on my home feed

For the home feed algo, it's treated as a cast from you. So anyone following you will eventually see it (depends on how engaging it is).

How much does home feed algo add in non-channel individual casts from people you don’t follow? 

One of the delightful things of Twitter was discovering random small accounts, would be cool to bring that magic back. Or is the goal to push everything towards channels?

Oooh nice to finally know it, always wondered how rc worked in here