Honestly, I think the answer is obvious … same as it was before … “Sub”.

Especially as kbin uses “magazine” for its communities, which means we need a short hand that is not specific. “Sub” captures the idea perfectly well and obviously carries over the Reddit analogy.

My vote would be keep “Community” as the long form name, as it’s a good description of what it is and for. Then short form “sub” because in essence it’s a subset of the total community.