I think it would be helpful to distinguish here between 'scummy' and 'anti-town'.
behaviour indicates that a player is more likely to be scum. These are very difficult to identify, can vary a lot from player to player, and make up one of the main challenges of the game! A particular player might be more talkative, or less talkative, or more relaxed, or more robotic, or just have a je ne sais quois that tells you that they are scum.
I don't think you can complain about other players being too scummy. If you often think players are
scummy
when they are not scum, then your job is to get better at scum-hunting.
behaviour is generally agreed upon to make the game straight-up harder for town to win. Things like:
- faking investigation results as town
- unnecessary claims
- refusal to engage with the game
- spamming
- no-lynching
Even here there might be a lot of be debate over the specifics, and scenarios where something anti-town becomes okay, but there is usually a certain amount of consensus, sometimes due to straightforward statistics (e.g. no-lynching on D1 generally makes the town less likely to win).
Because all the players in a game of mafia are either town or purporting to be town, for the most part they shouldn’t be doing things that are decidedly anti-town.
If your group of players are, then you can try to explain to them about why these things are bad play and why they make the game harder for town as a whole.
