Your comments

What's the difficult part? Can you elaborate?

Twitter has similar functionality, such that if you unfollow a user, their historic tweets no longer appear in your timeline. While I'm not saying FN has to have the same functionality its a very useful feature as there are times where artists still do post a lot of work that you'd not want to see.

It doesn't just have to do with import tool spam, it could be that your tastes changed, or you followed an artist because of just one picture but they ended up not producing the kind of content you expected.