There are, actually. Since Misskey’s culture are different from Mastodon’s, they have been implementing more features than Mastodon from the start, and Misskey’s APIs are different from Mastodon’s so there will be many weird quirks when accessing Mastodon (even weirder if it’s a Mastodon fork such as Glitch-soc, Hometown, Fedibird,… since they use older Mastodon versions as base) instances from Misskey instances (though Firefish devs are improving this by implementing Mastodon APIs and several Mastodon features). Also note that Misskey caters more Japanese users more than Mastodon, people who aren’t familiar with Japanese culture may also even Misskey userbase and features odd and different as well