Yes. You can easily spot them, either with masto in the name of the user instance or from the fact that the post or comment will contained mention in the @user(orcommunity@instance format.
Comment on Eight years on, Mastodon stubbornly survives
Wanpieserino@lemm.ee 2 months ago
Do we see mastodon posts here on Lemmy?
pseudo@jlai.lu 2 months ago
mesamunefire@lemmy.world 2 months ago
Yep all the time.
Piefed you can subscribe to individuals like they are communities. Works really well.
Draconic_NEO@chaos.social 2 months ago
@Wanpieserino
Only if those posts are to/mentioning a community on Lemmy or Mbin. Profile/public posts don't show up on Lemmy since Lemmy requires all post or comment content to be associated with a group actor (AKA the community/magazine).
derpoltergeist@col.social 2 months ago
@Wanpieserino @mesamunefire I'm writing this from Mastodon, and now you're seeing it.