You can’t follow Mastodon users from Lemmy. You can view their profiles, but messaging them doesn’t seem to work (I receive no notification of it on Mastodon) and it only shows you the comments they made on Lemmy rather than all their posts. You can @ mention Mastodon users in Lemmy posts and comments, and that works. And they can follow Lemmy communities and their replies show up in the post comments.
You can’t follow Mastodon users from Lemmy. You can view their profiles, but messaging them doesn’t seem to work (I receive no notification of it on Mastodon) and it only shows you the comments they made on Lemmy rather than all their posts. You can @ mention Mastodon users in Lemmy posts and comments, and that works. And they can follow Lemmy communities and their replies show up in the post comments.