Yes, as a user. If you go into Mastodon and search for Lemmy communities you can typically find them. There’s probably not all of them until a forced federation sync happens, which I’m not familiar enough to do as I also don’t use Mastodon, but technically it should be possible. I talked to someone posting from Mastodon inside of a kbin thread a while ago. They have to adhere to their limitations so their comments might be shorter and have to post multiple ones if they have more to say but it definitely works.

Kbin itself also supports toots in form of “Microblogs”.

I also just got my first reply notification again after several weeks. I hope that means that bug is fixed. :S