Posting the same thing to like 5 different communities at a time
I mean, I get annoyed when I see the same thing posted to two communities back to back, but 5 is ridiculous and extremely poor fediquite.
Edit: Seems the poster is some kind of spam bot. As one commenter pointed out, they seem to have spammed this to any community with "music" in the name. And it's more than shows up in the screenshot. A LOT more.
Not about this specific post (which might be a spam bot), but in general: If a post fits several community, I don't think it's something bad to crosspost it to them.
I'm of the opinion that you should pick one. If there's not enough engagement after a respectable period of time, post to another. I definitely don't think one needs to broadcast their thoughts/opinions out on all frequencies every time.
But the moment Lemmy/the average app supports cross-post consolidation or duplicate filtration, I’ll definitely agree. Even until then, you’re not wrong, but it does complicate recommending a best practice.