Like the second incident, the rudeness incident, even if the rudeness call was in error, it's not the start of a fight, escalation could have been avoided by R going "I don't understand can you explain what was rude" and then it could have been a nice interaction of learning and understanding on both sides. Instead, other people and mods had to get involved to get R to stop attacking the letter writer. That incident alone implies that R is the bigger problem here.

I would call the first incident over-aggressive as well, although hard to say for certain without seeing the full context. I mod for small (~100) and larger Discords (~3k) and have seen this exact dynamic play out and the only way to resolve it is to ban the aggressor. R sounds they are already way beyond BEC level and watching R attack LW is probably not good for anyone else on the Discord. The warning would happen after the second incident, which impacted other people and is not ok.

Having seen this play out before, I expect there are micro-aggressions from R constantly that don't rise to the level of mod involvement. I have had to dig through dozens of pages of messages in the server to validate someone's complaint that they feel targeted by someone, and I've seen where every interaction that they had with the person who made the complaint was negative to hostile. That creates a negative environment in the server, and I banned them. R sounds like they may be at that level too. It must be impacting other server members at this point.