Well I don't have a bad opinion about him (those are your assumptions), we just didn't agree on how a community project would/can work.
If however he did introduce intentionally a bug in kbin, just because of Mbin that's downright childish. The Mbin community does try to test all the incoming PRs (not just kbin sync PRs) on various instances apart from unit-tests, etc. We just do not want to depend on a single maintainer, hence a different way of working in the project.
He saying Mbin can't handle the kbin changes that is just not true (Odpowiedź: nie radzą sobie), at least we try to keep in sync (eg. for API comparability for upcoming mobile clients). But I'll leave it this, I'm not going to waste any more energy. I hope you understand.