And you know that how?
It could also be Q-team-leader or someone like that.
It could also be like my personal pet theory that the Q signature is not a namestamp.
Q told us his name was "Q Clearance patriot" and he said everything has meaning.
Some times he don't stamp it, sometimes he puts something after "the stamp".
Q, Q+, etc. could mean anything.
There is even one Q post from /GA/ that is signed DJT not Q.