"Machine masters" is a bit strong, IMHO. Hashtag use is strictly opt-in. Using a hashtag isn't about machines having power over humans, or humans having power over machines; it is about the harmony of human and machine language. It's a structure that bridges the divide, opening up the possibility of more fruitful communication between man and machine. I wouldn't say it's dystopic much in the same reason that I wouldn't say it's utopic; the existence of such structures is without virtue, because virtue is a byproduct of intent, and only the speaker can decide the intent of a hashtag (or the observer and the intent of the observation), not the hashtag itself. One could use hashtags for good or for evil, but it is not the hashtag itself that decides which is which.

As to the classification of the referent case, I don't have quite enough linguistic knowledge to engage that argument properly, but that's the first time I've heard it put that way.