No. Lemmy doesn’t allow you to follow mastodon accounts or any personal accounts, incl lemmy accounts, for that matter. Similarly, following a lemmy community from mastodon, while possible, generally doesn’t work well.

Kbin provides parallel interfaces to both threaded and microblog content that works well.

Generally though, it’s an unsolved problem trying to unify the whole fediverse into a single interface.

It will be interesting to see if lemmy will evolve to enable some sort of user based following. At the moment, keeping things simple with community subscriptions is part of how lemmy is developed.