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.
Dessalines is currently working on mod actions for Jerbia. Someone recently made a PR for moderator edits but it seems there was not enough interest and it was closed by the author. Better reports handling would be nice, but if you read the issue its not really clear how this should work. Private communities are on the roadmap for this year.
Karma is intentionally left out of Lemmy because it has many negative effects. Wikis make more sense as a standalone project, in fact Im working on something. Flairs are also potentially on the roadmap. For hashtags I dont really see the benefit as they would serve a very similar purpose to communities.