I'm not super familiar with the right terminology, but in short I think users should be able to follow whoever they want, but restrictions on how it is interacted with is fair game. I think following and replying to threads accounts is sort of a must, even if boosting and other functions are disabled. Also on favor of preventing non-replies from being sent to threads.
The real issue issue is interop with Threads means surveillance of users. Limiting the info going from here to there is essential. However a read-only mode that lets us get some value out of it is fine