UKC

I accidentally voted for the wrong grade on a line. The route doens't have many grades and I really want to fix it. How do I change my vote? seems to be frozen once you voted.

I don't think you can. On a few occasions I've done the same so I think it would be a useful function to be able to correct both the grade and start rating given. 

As yet you can't, but an improved system is being worked on

oh no

would it not be easy to implement that you simply click on the vote again and "submit" becomes "resubmit"?

I bet it's hard to design a perfect grade voting system.

One of the things I use the logbooks for the most is looking to see if a route is easy or hard for the grade

Yet voting on the grade after you've already seen what everyone else has voted is a cognitive bias. 

A similar problem could happen if you allow people to edit their votes. Many trad routes will feel easier on repeat ascents so people might edit their grade vote lower, leaving an inaccurate assesment for onsight attempts . As an example the guidebook description of Western Front (E3 5c) : "only e2 once you've done it a few times" 

Finally would be nice if votes could be tied to user profiles, or at least ascent style. E.g I don't care for the opinion on the grade of chalkstorm from anyone who headpoints or topropes it