Introversion

If you connect to a 4 player game (such that the game is full), and then the host changes maps to a map with a lower player count, the additional currently connected players are not kicked and can ready up as normal. When the game then starts, the extra players (ie players 3 and 4, if the switch was from a 4 player map to a 2 player one) show up on the scoreboard as normal, but act as though they were eliminated from the very start of the round, getting retribution powerups.

Don't the game end when going back to change the map?

Yes, it does.

I have seen games with 4/2 players in the server list.

Well how did they do that! D:

I can't reproduce.

I tried with Rabid, and we couldn't reproduce.

Shwart!!

Okaay, I'm not sure how this happened then... I'm pretty sure I joined a 4 player game, there were definitely 4 of us in the lobby, but when it started it was on a 2 player map with us 2 extra players getting the retribution timer straight away... perhaps if the host changed the map in between my server browser refreshing and me joining? I don't know if that would work though.