I thought it would be good if making a post with a URL alerted me if the same URL has already been posted to another community/ server. Then it could offer to make the body of my post a comment under that post instead.

What do you think, and do any technical people familiar with Lemmy / Piefed / ActivityPub know if suc h a feature is possible without huge overheads?

I prefer a functionality that detect cross post and show only the latest with an option to see the other duplicates. Since each community has it own rules I may not want my post to be a comment instead

One of the things I love about Mlem is their link cross post detection.

Yeah, I think that's the way

Yeah. Choice is essential.

That’s cool. They’re halfway there. If there was an option to choose one to have your post added as a comment it would be perfect imo.

Defederation of various forms would appear to make this a difficult thing to do.

There was a situation the other day where a post was called out for being a repost, but it was entirely possible that the OP couldn't see the original because their instance (let's say "A") had defederated the instance ("B") where the original poster was based. And all this was (or at least could have been) in a group on a different instance entirely ("C").

I won't say this makes it impossible, but it's clearly non-trivial.

PieFed has a feature pretty much like that. Once I drop a link into the new post form, it takes a while and loads a table with previous posts. Already helped me when I put in a YouTube like I rediscovered. But I had already posted it 3 months earlier... It's a very good feature to have. And probably not that difficult to implement.

Doesn't it already do that?

When using the website it informs me if a link has already been losted, while also searching for similar posts via title.

The app I'm using (Eternity) doesn't do that tho

Lemmy already does tell you this by title, so it would be cool if it did it by URL too

I think the Boost for Lemmy app does this

Yes, I would assume that defederated instances would just have to be ignored. I hadn’t thought of this. Good point.

They’re halfway there.

I have an open issue in their git for link detection before posting. Hopefully it is coming soon.

One of the Mlem devs said the detail is done by Lemmy, the app just displays it.