Flying Squid takes things personally rather often, and can get heated especially on controversial topics. I don't always agree with their behaviour as a user and as a mod, but tbh they are the more reasonable party in this particular exchange, though some of the responses are more annoying. The conversation could have easily ended like 1/4 of the way through by either of them. It's unclear if it's harassment to me, because I am reading it as both persistently acting childishly at times.
If they leave they leave, that's fine. No matter who is right in this, Blackbeard has no obligation to deal with stuff he doesn't want to.
Sounds like this was already resolved within the mod team. So if OP you're posting for history or were unaware, fine (but you ought to look for, ask and add surrounding context and actions, next time). If you're posting just to cause drama and a flamewar, shame on you.
Lastly, discord? Come on, we're on Lemmy here, harass people on a federated FOSS protocol like matrix! /s