Seems like an interesting effort. A developer is building an alternative Java-based backend to Lemmy’s Rust-based one, with the goal of building in a handful of different features. The dev is looking at using this compatibility to migrate their instance over to the new platform, while allowing the community to use their apps of choice.
Says who? Because that’s how the old platforms used it? I think we should really be moving past the direct influence of these corporate platforms and on the fediverse that probably means something of a well understood common language (like @user@instance or !group@instance). Hashtags were only ever a thing on twitter because the users just started using them and full text search was sufficient to handle it (this is more or less the position we’re in on lemmy). Direct support didn’t come till much later.