We had one. I can't for the life of me find it, despite the fact that it was within recent memory. But scrolling back through 2 weeks of comments and google searching the hell out of it doesn't turn it up. So I'll just sort of paraphrase myself, and hope the rest of it fills in:
I'm not comfortable with the idea. You're chummy with a user I have blocked, so me subscribing to you would piss me off and you subscribing to me would deny you a lot of valuable commentary. I'm totally okay being in control of my own experience, and totally not with being in control of anyone else's. Hubski's basic functionality is entirely user-facing and I think it's a big step away from that to do otherwise.
it's worth noting that Hubski itself tracks blocks and ignores and that, should a user or domain end up ignored enough, they cease to get posted. I'm not sure what the thresholds are on that, however, and it's used exclusively for spam control, not behavior moderation.
I would argue that the act of seeing and dealing with trolls is a valuable tutorial for the new Hubski user.