You can read FEP-1b12 to understand how Lemmy federation works. To make it short, these Announces are to let community followers know about all the posts, edits, votes etc which are happening in the community. You can check the audience field to distinguish from Mastodon-style boosts.

just a guess, but looks like it's listing every upvote as a reblog by the community?

the list could combine all the reblogs by the same user into a single line, no need to show multiple I think

You mean 'thorn in my side'

how many times did you edit that post per chance? Lemmy seems to boost edited posts for some odd reason

see https://brain.d.on-t.work/notes/9md8phwlkzlj0xe9 and https://brain.d.on-t.work/notes/9m1y542jlg8002bj for it happening on my misskey instance hacked together to support Lemmy federation