Is it impolite to crosspost someone else's post to another community on Lemmy without saying anything?

cross-posted from: https://piefed.europe.pub/c/asklemmy/p/266879/is-it-impolite-to-crosspost-someone-else-s-post-to-another-community-on-lemmy-witho

I feel like on mainstream social media this is done pretty thoughtlessly and it's a norm but on Lemmy, with the much smaller userbase, I kinda felt like... it's like riding on someone else's coat tails? Or is it just me?

Edit: of course if it's artwork or text, obviously then I'd make it explicitly clear it's not mine but I mean news articles, memes, things like that.