https://www.reddit.com/r/golang/comments/ppluux/peter_bourgo...
which links this document:
https://docs.google.com/document/d/1exmMfbgVCz3dRXOOlfUCYeiX...
which looks an entirely reasonable reason to formally ask someone to knock it off and take some time to chill. From the document, it seems that he has a policy of ignoring Slack moderators, took the fight to Twitter when his Slack account was temporarily deactivated, and has a pattern of such behavior.
If that document is to be believed, the punishment was not excessive and arbitrary. He got a temporary Slack ban, which was appropriate and measured, and then chose to continue escalating.
There's also this reply:
https://twitter.com/ahmetb/status/1438653799724294144
> @peterbourgon Many of us here have respect for u from a technical standpoint and learned from your talks/code. However it’s wrong to troll people on slack (because “this is internet”) and call them names on twitter for no apparent reason. I hope you can stand back and understand the mistake.
For what it's worth, I actually think it's a good sign that the CoC is equally enforced against a drafter of the CoC - the alternative is that there's a group of people who are sufficiently in the in-crowd that their behavior is the definition of what's acceptable and they get to do what they want. It's absolutely possible to abuse the power of CoCs, but this seems like the exact opposite.