I think it’s more of an etiquette problem than a feature problem. Posting the same thing to many different communities should be deleted as spam. The multipost in your screenshot is certainly spam. Report that.

If you are want to post something and don’t know which community fits best, or feel like multiple could fit, then just post your thing tone community. If other people find your post especially interesting, they can crosspost it. To me, cross-posting your own posts is a sign of an overinflated sense of self-importance.

Multi-comms are a planned future feature IIRC.

Piefed web interface does stack comments if cross posted, so I’m guessing the poster isn’t bothering to cross post if it isn’t showing that way in Intersellar.

In Lemmy, no way.

In Tesseract (yes, that Tesseract!) there was a partial way, but only if the posts happened to come in as part of the same batch when accessing the instance. db0 helpfully made a fork of that, but the community outcry was so enormous that several instances simply dropped support of it entirely rather than switch to using that fork.

In PieFed, partially, but only for those sharing the same URL (like these examples probably do?) - so text-only posts do not qualify.

And then 3rd-party apps add a whole new dimension to this, by replacing the Lemmy/PieFed/PyLova/Mbin front-end with their own stuff. Note that Voyager provides only rudimentary support for PieFed. Overall, app support for the improvements that PieFed makes over Lemmy is still fairly shitty, sorry to say - note that you can tweak some settings in a web browser (like user blocks & such that are entirely impossible in Lemmy) and then that affects your using the 3rd-party app on a more daily basis, but many of the more advanced features of PieFed/PyLova are still inaccessible from most 3rd-party apps. See this wiki page for more details - like “Crosspost comment merge” is only supported in Interstellar, and some features (like a mod locking a post) is not available from any app, iOS or Android.

Lemmy is the same way - reducing such crossposts an extremely often-requested feature, for both software platforms, but so far I think only PieFed accessed via a web browser can do it even partially. Or certain 3rd-party apps (not sure which ones, though I’ve looked at several FLOSS offerings and did not see that - maybe only paid ones do?)

Lemmy doesn’t really have much in the way of an “algorithm” and it really shows with stuff like this.

Mbin can combine posts like that and show comments from all of them, but I think it shows all posts in the main post view, it only combines the comments. I really hope in the future Lemmy combines crossposts into one posts. It’s something an app could do. But I’d love to see it in the default UI so it hopefully encourages all apps to support it too.

Connect app stacks them together and shows the replies from each thread in batches

Sounds like a good feature request, to either Lemmy in general or whatever that app is, or both

I think some mobile apps get rid of the duplicates, although I’m not familiar with which ones do that. Unless someone else replies here, you could try posting to !lemmyapps@lemmy.world