Maybe they could not only allow you to comment others but also detect the ones that came in a party. That way the system would have it easier for know who can't vote who...

So, how? Similar to the alliances when you join to a CT, that autoassings you in one. Here in the party made it would be similar but using any other thing. For example, imagine a dungeon of 4 people, two groups of two premade persons. It would show for example that both DPS entered there in a premade party by showing their name in the same color in the party list, green for example. While the healer and tank have other color showing they were from another premade.

Of course, this distinction could be something else, not only the color name, it could be just to share a symbol aside of the name, a little bar with a color aside of the class icon... Options are too many...So if Square Enix is able to detect the groups of premade, they are also able to allow you to vote everyone except those who share your premade... It is basically a classic "if / else" ...

If the partyset is not the same than own, then put the available command/method/option for vote, else no.