Sadly you can't follow a user (yet?). Some OC posters create an extra community for their own content, which you then can subscribe to.

You can bookmark the profile of a user in your browser if you're using the web ui.

I personally use sync for lemmy. It let's you favorite a person's page. Not sure if that's universal, but it's kinda like following them.

I wish

You can, if you do it from a Mastodon instance.

Kbin lets you follow users, lemmy can't and the devs won't add it