Is it dumb? That's fine I don't give a fuck. I will continue to block people who post the same article to multiple communities, in a Federated system like lemmy. I don't want to be browsing my feed and see the same article two or three times in a row from the same user, it's ridiculous and a holdover from Reddit where people would attempt to post things in multiple places to double or triple their karma. That doesn't exist here in the same sense so there's really no need for double or triple posting. It doesn't take a fucking genius just put on your big boy pants and think about it for a second.
Or posting in multiple communities gets different views and replies, so they can see multiple points of view. Posting to Politics is going to get different responses to posting on News.
Only subscribe to what you want to see. Nobody is forcing you to read posts multiple times.