This is kind of like my answer to people who ask me if I am a vegetarian. I say "Yes, except when I eat meat."
So, IMO, given the varieties of writing engaged in, the number of members (many of whom come and go) I don't think it would even be possible to know how many are here who are self-defined as "not writers."
I know of a couple. But even those I suspect of writing.
Personally, I can say there have been months in which writing seemed so distant from me that I considered whether I ever would write again. But that consideration does not last very long. And all during that time, I was both posting here, and keeping my blog updated once or twice a month.
Doesn't count, does it?