The Day phase on a Mafia game is where the bulk of game play occurs. Players are permitted to talk in thread, voice their suspicions, defend themselves from said suspicions, and discuss any results of night actions performed, and vote players they think are scum. Posts made during the day cannot be edited, except when moderator permission is given to fix things like format - actual content cannot be removed. Days end when the players come to a consensus and find someone to execute. Some mods place deadlines on the day phase, which ends it at a set time rather than when players reach a majority vote. If there is a deadline and no consensus is reached, the day can end in no executions.
Traditional Mafia games don't permit scum players to talk out of thread during the day. However, SA mods almost always allow scum to communicate during any phase of gameplay.