Redoing my ticket T122770 since it seems no one's paying any attention to old ones.
It would seem that headless clients count as players on a dedicated server. This results in several issues, such as but not limited to:
With "persistent = 0;" in the server config, the mission does not end when all actual players have left, as it would without the HC connected.
If the mission has already run and ended since launch of the server executable, the lobby timeout will count down without any actual players connected. Due to this, when a player connects after the timeout, the mission starts immediately without allowing the player to choose a role.
The player count in the multiplayer server browser shows an incorrect amount of players connected to the server; This is due to the value including HCs. A server owner may easily fake a populated server by connecting many HCs to it, either intentionally or unintentionally.