I guess my point is that the federation issues seem to affect specific users, then. I poked at threads some more until I found nearly exactly the same issue with Cletus - history ends ~a month ago, more recent comments haven’t federated.
If it’s not an issue with having been moderated on kbin.earth, it still seems oddly user specific, and at least possibly time correlated for the two examples I’ve found so far. That might make it easier for blued_gear to figure out more about what goes wrong.