Sorry, I meant to answer this directly, but I'm still catching up.
In the original FEP, I tried to address the FEP namespace from w3id.org. There's a lot of good reasons to use it. But I'd hate to have to type `/fep/3b86` over and over. It's not very semantic, so I went looking for something else.
What do you think of using `w3.org/ns/activitystreams/#Follow`? Are those IRIs off limits for some reason? If not, it seems like a pretty good fit.