I’ve never used Misskey but used various Misskey forks for about a year. I ended moving back to Mastodon. In my experience, the forks are very good at all the extra razzle dazzle they add (MFM, emoji reacts, drive, etc.) but often aren’t as good at the basics. I’d pretty routinely have federation issues, missing posts from my TL, and posts that would just repeat endlessly in the TL until I reloaded the page. And those are problems I experienced on every fork I tried. I found that stuff more of a minor nuisance at first but it got pretty old over time. It’s been a few months since I migrated back, so some or all of those issues could be fixed or improved by now too.
Also, app support isn’t great. I think most of the forks implement basic Mastodon support now that will allow most apps to work. But the downside is you only get Mastodon functionality in those apps and not the extras.
This really sucks for him after all it took to get back. Glad he’s not gone for the season.