I sympathize, and I understand how it can be demoralizing to put in a lot of effort into an answer only to never receive any reaction or feedback at all. It can feel like you are writing into a void, and that's not very motivating. I sympathize with the problem you've identified.
Let me suggest a different way to address the problem. Rather than trying ...
Some users ask a question and disappear. Maybe they found an answer elsewhere. Maybe they don't care anymore. Maybe they they lost the cookie to their account. There's nothing you can do about that.
Users with less than 15 reputation cannot vote.
Any user can accept an answer on a question they asked (except during the first 15 minutes). They are not under ...
In those cases, you cannot accept an answer. A comment is not an answer, so you cannot mark a comment as accepted.
Instead, I recommend you do one of two things:
Write an answer yourself that answers the question (incorporating the insights from the comment). Then, mark it as accepted. This ensures that others who come across your question have a nice, ...
Given the current state if the system, I think the answer is "nothing can be done".
As long as there are any votes, you can not know if the asker voted.
There is no way to force them to vote or accept.
All you can do is not to answer questions of users that you know to be "ungrateful".