Does something like this exist? As far as I can tell, setting something similar up would require:
- A dedicated Lemmy instance for Mastodon tag-based crossposting (probably, since most existing instances probably don’t want to clutter their instance with thousands of script-generated communities)
- Some kind of form on a site where users who want to follow a Mastodon tag that is not already set up as a Lemmy community could submit the tag they want added, which would automatically set up:
- A Lemmy community for that tag on the aforementioned instance, and
- A Mastodon hashtag bot that automatically crossposts all posts with that tag to the linked community
Yes, but we’re talking about a bot doing this according to the hashtags in the post. The original post, having never been posted to a lemmy community as you describe, can never be interacted with by lemmy users even if a link or cross post is made.
Kbin has a separate tab within a community called “microblog” I think. Any hashtags set by the community are automatically followed in the “microblog” feed and can be fully interacted with.
This doesn’t bring threadiverse content into mastodon, but it does bring kbin users at least, into mastodon.
And with the @ing of lemmy communities, you can post from mastodon to lemmy. There’s some work to be done, for sure, but I think we’re close to a decent solution.
But also, 100% compatibility would be odd, wouldn’t you just switch platforms if you wanted the different functionality.
I don’t think there’s much point to a fediverse if there isn’t decent compatibility between platforms, especially if they both comprise plain text posts and replies.
Beyond that, I agree, I don’t think these issues are hard. In more detail, a central issue is the simplicity with which microblogs format their feeds: everything is a post which are all assembled in a flat feed, with threading replies together being somewhat optional. There isn’t a sense of structure as lemmy/kbin have, with communities > posts > comments > replies. To me this is brutalist and unnecessary and limits the ability with which other platforms can be integrated. As mastodon completely dominated the fediverse, these limitations are actually somewhat severe, as a large part of the fediverse is constrained by this often without even knowing that there are other options.