We have a new user among us who I recognised from English Language and Usage as one who never marks answers as correct, even in one case where they said "Exactly what I was trying to find". At least they added "Thankyou".
While this may not bother some of us, it rubs me the wrong way. Maybe this says more about me than they.
The extra 15 rep is not so important to me. With n00bs you often get that. But usually they get the hang of how things work if they stick around. But this user has been on Stack Exchange for over a year. Multiple senior users have asked them to select the answer deemed correct, but there has been no change observed.
Not everyone here follows the behavioral norm for bicycles.SE; this community is in general much more gentle than robust communities such as the main site, Physics, Maths, et al. But one cannot really complain if a user is following the established SE norms. But this user doesn't.
So my question is how can this person be pleasantly persuaded to follow the SE norms?
A bonus question is should such persuasion be attempted?