This is why I think previews should be a downsized version of the full image and nothing but that, especially knowing many people cast their votes based only on what they see on the poll's previews.
It should be applied to every comp, even 2.0 comps, let alone an unedited shots comp.
The way it is now, not only the voting's probably not fair for all competitors, but there's also nothing stopping anyone from spicing up the previews with illegal tools, just to get more votes.
The way I see it, it's one simple rule that makes it fair for everyone, causes no harm to the comp and prevents possible problems.