https://social.technoetic.com/users/steve/statuses/111331622962509323
The list is longer than that, but it would need a long form post to cover all of what would be needed to have something similar to the Mastodon UX. This is easy to confirm if you compare the APIs.
It's possible to implement some of those features in a ad hoc way using AS2 data structures, but I believe many UI developers prefer an API that's standardized across server implementations.