I agree with you that it is the most healthy method to not interfere with anyone's decision for a long-term relationship.
My viewpoint is not to manipulate someone or try to change people's decision but to come to a decision that is in harmony with us and others.
We face situations like trying to negotiate our rent with landlords, asking for discounts on products or having arguments with people and our family.
So what's wrong with a technique which helps them to listen to our opinions more attentively and with reasons, instead of ignoring them, resisting them.
This is not some kind of magic trick that can manipulate someone to do whatever we want, it is just a way to communicate better with people, and how is communicating with someone in a better way ever wrong?
Haha, YES! Perfectly stated. Surely, when you are negotiating with landlords honed communication skills are of great assist, and generally in all your examples here
To not become pulled over the barrel is indeed a good skill to have, and this starts with communication. But yeah, even when I prefer saying nothing in more personal relationships, and let others have their learning lesson, this is also a kind of a communication method.
ALL is communication! :)
All is communication, even when you decide not to say anything, a silent communication.