It’ll try to render it, even if just as markup (like if you try using and Latex markup for math).
The federation with Mastodon is mostly one-way: We can’t see or comment on Mastodon posts, but Mastodon users can see and comment on Lemmy posts.
Mastodon’s like Twitter… its posts wouldn’t fit in the Lemmy UI well. Though I hear kbin works well with both Mastodon-style and Lemmy-style posts.
It’ll try to render it, even if just as markup (like if you try using and Latex markup for math).