On the "is it ok to give players auto-successes on persuasion rolls for good acting" discourse, everyone is missing one crucial point, which is that skill checks are lame and boring.
If a player says, "I want to search behind the tapestry" and there's a secret door behind the tapestry, am I going to make them roll perception to find it?
If players are presented with a puzzle and one of them works out the answer, should I make them roll an investigation to determine if their character would discover it?
If players have a good argument and they're being reasonable with their request, especially if they're going with it in character to a persuadable NPC, sometimes it's better not to roll that check and just go with your gut