Voteless is a role modifier that simply disallows the player from voting. If the player tries to vote, that vote will not be counted by the moderator.
This modifier usually appears in games where it fits flavor, or when vote-based shenanigans are in play (for instance, the weight of each player's vote is unknown).
Use and Power
Being rendered voteless is one of the worst things that can happen in a game. Without a vote, a player cannot influence the game beyond the weight of their words, which the other players may or may not follow. Many players will simply refuse to play in any effective capacity upon finding out that they are Voteless. Thus, use of this modifier is not recommended.
This is even the case if the Voteless modifier is combined with a power role (i.e. Voteless Cop). While the role now has a cool power attached, the Voteless player must essentially wait for the Day to finish before it has any relevance.
For obvious reasons, a Voteless player is not counted as a player during game balance (unless it has a power role attached like above). However, the one upshot to being Voteless is that if a killing role feels some need to kill a Voteless player, the death of the Voteless player does not count against the Voteless's faction in terms of who controls the Day game.
See also Tree Stump.