is about liking bands that aren't well-known / don't conform to genres / aren't popular, post indie is about liking bands, regardless of how popular they are.
Perhaps not on purpose, indie kids tend to scorn popular music, and measure indie cred
based on how unknown their favorite artists are. You can't be considered "indie" if you mostly listen to popular music, even if you genuinely like the music for your own reasons, and don't care about other people's opinions of it (which was supposed to be the point of indie).
Post indie comes after indie, and fixes this problem. Post indie cares neither positively nor negatively about the popularity of music. It is indifferent. If you listen to music because you genuinely like it, and not because you are conforming to any group or genre, then you're post indie.
Indie Kid: Yeah, I used to like Coldplay, but then they got too mainstream, and I couldn't stand them anymore.
Post Indie Kid: Soo... you say other people's opinions of music don't matter to you, but you don't like a band because other people like it..? Does that make you lonely?
Indie Kid: ...Sometimes...