Google Translate:
First of all, the ActivityPub system is not suited to something like Misskey, which flows at lightning speed.
It was originally designed to connect blogs, small-scale SNSs, and wikis.
How can it handle the TL hell where tens of thousands of requests fly in per second?
It’s based on the idea that it would be nice if various small services could send each other updates, so it’s quite costly.
Misskey has been around for a very long time. Also a lot of comments here would probably be their own posts on a microblog platform.
Don’t get me wrong, it’s not a good news by any mean, but it’s still not so bad if users who want to stay on the Fediverse switch to a fork.