Rather than something complex like this can we get the down and up vote arrows separated? Something simple like putting the arrows on opposite sides of the user's name would be fine. This will stop fat fingered people like me from accidentally down voting a post when I am reading on a mobile device.

This is only a problem because you can't modify your vote. On Reddit, you can change your vote any time before the thread is archived.

It is a problem even if you could modify your vote as a lot of the time I am not sure if I have up voted or down voted a post.

I love HN and its low fi design, but this is the one thing that I think takes away from the community spirt here. Intent should always be clear.