I see voting as a way of encouraging quality and giving a boost to the poster, anonymous or not. Maybe that person is worried (as a newbie might well be) that their code is not up-to-scratch, and they would get ridiculed or even flamed. So a few ++'s might boost that person's confidence and encourage them to sign up for real.

I think often, even very lame code might deserve that ++ because at least the poster has bothered to ask, and the question might raise some interesting points.