You are very right, when I comment to someone and they ignore it, I usually don't comment again because after all I am writing it for them to see. The vote is not very important to me, but the answer is. Especially when I ask something. After all, I don't just write "good post".
I think you have to give them advice once and then let them decide what they want to do. Then they can do whatever they want and they have no right to hold a grudge against you lol. It's not like you're making a mistake.