The rule of thumb I use in developing web applications is that when submitting a form causes some kind of an action, such as voting or buying something, the script should apply the changes and then redirect to an appropriate url that shows the results.

This would eliminate the "double submit" problem as well as the "useless bookmark" problem, at the cost of a slower response time to such requests.

I haven't poked through the slash code base (Update: or Everything's), so I don't know how difficult it would be to make such a change in this particular case.