He is kept on here by the mods as there are always people that are stupid enough (or new to the forum) to respond, which is what he craves. Shouldn't judge too harshly as you don't know why people require this kind of online attention, but yes it certainly ruins the forum.
Whilst people respond the posts increase, and in turn website hits so the mods will keep him here regardless of the absolute irritation to some of us (maybe a lot?).
I can only advise you use the ignore function but when most of the comments end up being a response to whatever nonsense he decides to post it kind of becomes worthless.
Anyway I'm grateful for all the other comments on this forum, most people are genuine even if I don't agree with them all