I'm not sure this would be a healthy addition. It promotes the wrong kind of atmosphere, and I'm not sure I want to see stalking being made any more convenient than it is. Which in itself brings about its own issue, there are users out there who don't know much about respecting boundaries. Who feel that if others people don't reply to them, yet post as normal; they are being ignored. I've seen it time and time again where users really get unhealthily attached to others users and I feel that this addition might actually become more like a breach of privacy than anything.
There is also the whole idea that we want to promote ourselves as a community, I think that if groups or small cliques of users start just following one another's posts, PC could become too internalised and introverted within said groups. I think a feature like this promotes the atmosphere that "I only care about what XYZ users have to say, so I'm just going to subscribe to them." As opposed to actually being more well-rounded and organically coming across posts you enjoy.
I for one, wouldn't be too comfortable with members following everything I say either. You can do it by going to one's profile, yes, but this addition makes me feel uncomfortable for all the reasons I stated above, and I feel it would cause a shift away from the desired community spirit we want here.