Fairly often, I find myself using various StackExchange sites while on trains or buses, connecting my laptop to the internet via my mobile phone. Given that I'm on the move, connectivity varies from great to terrible and back again. StackExchange sites don't seem to work all that well with lots of dropped packets, as sometimes happen, for example it takes a long time to display the red "error occurred" popup on some actions.
When marking a comment as useful, there is a visual indicator of if the marking has worked or not. When you first click, it looks like this:
Then when it has been accepted by the server, the marker changes slightly:
It's therefore easy to see if your comment mark has worked or not, and hence if you can close the page or need to leave it open to wait / retry.
When voting on questions or answers, there doesn't seem to be any easy way to tell if the vote has been received by the server or not, so you don't know if you can move on to another page or not.
Would it be possible to have some sort of visual indication, in a similar way to comments, to allow you to know if your vote has made it to the server or not?