I am a user of Stack Overflow. It is perfectly appropriate to refer to me as a SO user.
However, I am not a "stacker".
I do not stack anything, unstack anything, or restack anything as a career. I don't stack anything unstacked or restacked, or unstack anything stacked or restacked, or restack anything stacked, unstacked, or restacked, or repair anything stacked, unstacked, or restacked. As a career, I do not do that.
And really, cutesy names for the users of a web site just reek of boosterism. Is it too much to ask that we just not go there?