It doesn't even really have to be AJAX. You could solve the problem just by setting up an #anchor so that when the screen reloads after voting, it just the user back to where they left off.
that doesn't solve the problem that I (and I assume others) habitually press the back button when I'm done perusing comments in order to get to the main page. At this point when I press the back button it goes to a slightly older version of the comments page- and various other oddities.
I run into this problem all the time--not good for diminishing by reload-addiction! It would be nice if pages included some js to rewrite history[1] via dom, so that we could always see the freshest versions of pages.
[1] It pains me to advocate breaking the "show me exactly what I was just seeing" semantics of the back button, but I think in this case the user clearly conceives the back button as "show me the abstract resource I was just seeing."
