I consider voting pointless according to my "utility function," if I am measuring the benefit to society that results from the fact that I voted for a particular candidate, basically because I have to take into account 1) the probability that I am mistaken about the better candidate, and 2) the bounded character of my utility function, which means that a small probability of affecting the outcome really does mean small total utility. Given those facts, if I choose from that utility function alone, from a baseline position I would not vote at all, and I would be willing to vote for any candidate, including Trump, for a relatively small sum of money. However, I am not a utilitarian in the first place, and apart from that, even if I were, I would have to take into account the effects on my character, as in your argument.

Only in the simplified abstract model of the situation. In reality things like the ability to brag that you did (or did not) vote for that bastard (or that bitch) or, say, even minor shifts in self-perception are worth more than 10c. The point is that if you don't know my value system you cannot say what would or would not be rational for me to do.