I think that your vote can count even if, in retrospect, it changed nothing, so long as votes are interchangeable and anonymous.
I think that's the crux of the issue. My take was to assign a mapping between people and votes such that your vote was in the "excess" portion and thus didn't matter. But just because such a mapping exists doesn't mean it is fair or valid to assign it. Instead I imagine it's a statistics problem where all mappings are possible, which leaves you with a non-zero but tiny "contribution" to electing the winner.
And if you voted for the loser? Then I think the contribution to voter turnout mentioned in the post comes into play. Again a only very tiny amount, but non-zero.
Then finally social issues likes signaling status and desire to belong to a group probably are pretty big factors, maybe bigger than the above "real" factors.
In the end I think it's possible to justify voting or not voting depending on your values, particularly how you value your time relative to these fuzzier benefits.
To a large extent, I vote to avoid regret-- if someone I detest gets in, I want to feel that at least I did a little something to not let that happen.
For many years I've been interested in the "paradox" that your vote tends to never alter the outcome of an election, yet the outcome is in fact determined by the votes. I wrote a blog post about this and tried to explain it in terms of emergence, we as voters are just feeling what it's like to be just a tiny part of a much bigger system.
Then I tried to explain that "voter turnout" is in fact one of the most important metrics for an election, it determines the legitimacy and stability of the process. So therefore even though your vote won't determine the winner, it will contribute to voter turnout and thus is productive and useful.
http://www.kmeme.com/2010/10/why-you-should-vote.html
However I don't find my argument all that compelling, because even voter turnout is going to be approximately the same whether you vote or not.
In the post I bring up littering as something else where your tiny contribution adds up to be bigger result. I personally would never litter on purpose, yet I often skip voting because it seems like it doesn't make a difference. Is voting rational? How do you justify voting or not voting? My post was non-partisan so I'm soliciting non-partisan comments, trying to focus on the theory behind voting in general.