I was really surprised to hear this, so I dug a little deeper. It looks like an honest mistake.
Here's what their admin said:
We unintionally did until about 8 hours ago.
Lemmy.ml has a ton of bot crawlers in its nginx logs spam fetching posts, so I added the bots to an nginx block. Turns out one called kbinbot wasn’t actually a crawling bot, but their federation requester.
If we don’t respond quickly, its because we have notification backlogs that are months long at this point.
Getting caught in a large rainstorm in the evening while on a mountain trail with 3 more hours of rocky descent to go.