There is a phrase going around now, dark patterns, and I am glad somebody named the thing.
You know them even if you have never heard the term. The unsubscribe link that hides. The cancel button greyed almost to invisibility while the upgrade button glows. The pre-ticked box. The bit where declining a discount means clicking something like no thanks, I do not want to save money.
What I keep coming back to is not really a moral point. It is closer to a business one. A trick is a debt. You are borrowing trust from someone who does not know they lent it, and the terms come due later, all at once.
It works for a while. The metric moves. And then the customer works out what happened, and what they feel is not annoyance. It is the quieter, longer thing you feel when you realise you were handled. People forgive a company for being bad at something. They have a harder time forgiving a company that was clever with them.
I have talked a few clients out of these, and not by moralising, which never seems to land. I just ask what happens on the day the person realises. Every dark pattern has that day built into it. You are trading a number now against the moment someone finds out.
I have no problem with persuasion. Design is persuasion. The line, for me, is consent. Persuasion says here is why this might be good for you. The other thing arranges the room so you cannot easily do anything else. One of them you can stand behind later. The other you spend a long time explaining.