I was playing on a server when a teammate named the default 'Deuce' started griefing. I pressed tab to check the player ID to votekick, but there were multiple 'Deuce's on my team. I did not know which one to try to kick so he went on griefing.
Either forcing unique names or displaying the player ID as well as name above their heads would fix this.

I think i was in that server... Was he using hyperspeed and throwing grenadas? Was he blue? And that is a good idea

I thought the number to the left of everyone's name is their ID.

Although, I tried using the id number once and nothing seemed to happen

Well they're generally using hyperspeed and infinite grenades Stickeys.

Until something is done about the Deuce situation, I think you should monitor the kill counters. If a Deuce is getting a lot of kills, that is most likely your griefer. Of course, that won't ALWAYS work.