for those who don't know, bob black is a long term anarchist author and controversial figure. Since the 70s he has been involved in a variety of altercations, the most notorious one being with jim hogshire (not an anarchist) during which both parties called the cops on each other.
he is notorious for crossing lines of behavior that anarchists commonly accept. he is mean. his critiques are usually a mixture of relevant information and irrelevant nitpicking. and he is eager to take on what he considers to be anarchist sacred cows, like professor graeber, ak press, murray bookchin (ad nauseum), etc.
those last two tendencies are two reasons why some anarchists continue to see value in black's participation.
added to that is the respect some feel for the author of cogent pieces like "the abolition of work", and anarchy after leftism, as well as some people's difficulty in sympathizing with the strident and kneejerk attitudes and complaints of many of black's critics. also, he is frequently/occasionally funny.