Are cases of charm, suggestion, dominate monster and the like different?
If Valindra had successfully charmed the player in question, could they still scream out she was a lich and try to attack, even though they viewed her as a "friendly acquaintance"? Can charm always be worked around by a resourceful player since they could think their friendly acquaintance had been replaced by a doppelganger, or maybe had been cursed where the only way to save their soul was to kill them before they committed some evil act?
I know this has moved on, but I'd like to answer cleanly. Yes, these are different, but each in different ways. The difference here is that the game has rules that are now limiting the kinds of available actions when compulsion effects come into play. Much like you cannot use the Attack action to make a melee attack on a target if the target is not within your melee reach, these effects add constraints to allowable actions in very specific ways. Their existence, and the fact that they may constrict allowable action declarations, doesn't translate into anything more general -- these effect exist only within the embrace of the compulsion effect, much like the restrictions on when you can employ the Attack action only apply there.
That said, suggestion is pretty straightforward -- you can do whatever you like so long as you can do it while following the suggestion. This one is very close to dominate in that it requires a specific action. Nothing more is necessary, so long as you abide by the specified action. Dominate is pretty clear as well -- the player loses all control over their character and it becomes a limited NPC for the duration. I usually leave the player in charge, and just direct the actions, if it comes up.
Charm person, on the other hand, allows a huge range of possible actions. I believe someone asks later how one acts like a friendly acquaintance, and that's my touchstone -- my idea isn't any better than my players', so I'm going to let them decide. If something seems very odd, I might ask them to tell me what their character is thinking here -- not because I'm going to deny the action, but because I'm curious. Every time this has come up (which, honestly, is less than a handful), the player has a perfectly valid way to think about it that I didn't consider. This reinforces my preference for letting the player decide how to act under charm effects. I see that examples such as attacking the charmer are proposed, but this really goes to 'don't play with jerks' rather than an adjudication style. If you feel you need to assert control over your player's ability to play their characters because, if you don't, they'll turn into rage machines that auto-attack people that charm them because you don't worry much about metagaming, I'd say find new players. I don't worry about metagaming, and my players are present to play a fun game. I don't think argumento ad jerkum is a valid point, because it can be applied to any position, including anti-metagaming (as has been pointed out in this thread). Anti-metagaming doesn't prevent this, not gaming with jerks does.