At our table, if a player suggests doing something that really seems to go against the character's alignment, the DM will just reframe the action as a question, in a way that shows where the DM sees the conflict. The player can then say, "yep, that's what my character does," or, "wait, no, now that you mention it, he probably wouldn't do that..."
Example: "I'm going to kick the guard in ribs until he answers my question." "So, you're going to torture the guard?" "I guess so."
It's up to the players to do their best to play their character in a way that is consistent. It is up to the DM to frame a world where actions have consequences, including angering deities, local authorities, etc. If a player has a concept that they are struggling to play consistently to the point where it's taking fun away from the table, it doesn't hurt to talk to the player about ways to change the concept to fit the character the player actually wants to play.
But some sort of mechanic that says, "You're not roleplaying well, so your character will be penalized mechanically (as opposed to in-game consequences for in-game actions)," feels a little much and an unnecessary source of conflict.