I've noticed a few users who submit a fair amount of well-received questions, which attract a fair amount of answers, but rarely -- or even never -- accept any answers, no matter how thoroughly researched and sourced.
As a matter of etiquette, is it best to just ignore this? No one is entitled to a little checkmark, obviously, but I suspect that the pattern may discourage thoughtful responses.
A general comment to note how acceptance works, and recommending that it be done, would be reasonable. Many users don't understand the purpose of acceptance, nor when and how to use it.
Informing users of the tools available in improving the Q&A they have any involvement in, and encouraging their positive use, is good practise. It is not the intended use of comments, but we seem to let slide a lot more that's definitely not within bounds.
A comment requesting acceptance of a specific answer, or even to a specific question, would not be appropriate. Why they have not accepted that answer, or any answer to that question, is for them to resolve before they can be expected to do it.
Requesting a specific acceptance is either pressuring someone to make an uninformed decision, an abuse of relative social position, or pressuring someone to change their decision, which is not welcoming or respectful (both requirements are in the Code of Conduct).
I suspect that the pattern may discourage thoughtful responses
No, it won't. Upvoting should be seen as the primary source of encouragement for thoughtful responses. Whether the OP finds them acceptable should be of a little concern.
That said, I do not see anything wrong with a comment seeking to find out what makes a particular answer still not acceptable despite its apparent quality — for example if the answerer's ego feels injured by not seeing their answer accepted.
I agree with the first two paragraphs of the answer by Nij: a general comment explaining how acceptance works, particularly to relatively new posters or those who may not understand the mechanism, is acceptable.
I do not agree that "A comment requesting acceptance of a specific answer, or even to a specific question, would not be appropriate." at least not in all cases.
I agree with the part of the answer by Greendrake that says:
I do not see anything wrong with a comment seeking to find out what makes a particular answer still not acceptable despite its apparent quality.
I do not agree with the part of that answer that says:
Upvoting should be seen as the primary source of encouragement for thoughtful responses. Whether the OP finds them acceptable should be of a little concern.
If an acceptance were not designed to be of concern to an answerer, it would not carry reputation points, as the upvote of a comment does not.
When a user, particularly an apparently new user, has posted a "thank you" comment to an answer, I have sometimes responded that the best possible thanks is an upvote, and if the user thinks the answer is THE solution, acceptance. I include a brief explanation on how to upvote and accept, and usually mention waiting a day or so before accepting in case a better answer is posted. This seems acceptable to me.
I have not noticed a particular asker who never or rarely accepts an answer. But I do not se why a single polite question about such a practice would be unreasonable. Pestering o repeatedly bringing up the issue would be, I think.
