AO3 where this happened has many vistors/readers who don't have/want an account because they're not writers and don't see the need, or haven't yet got an invite to create an account, so I'd be cutting off a lot of potential comments for the sake of 1 or 2 people's spite. I could screen anon comments and if this happens again I'll go that route for a while, but thankfully this is a rare occurrence for me which is why I was so taken aback