I occasionally post comments with potential answers in them. I usually do this when I'm not sure if my answer is what the OP is looking for. If the OP doesn't respond, there are no other comments about my answer, the question does not attract much interest, or others have already posted answers, then no further action. This does have the drawback that in some cases it may discourage others from answering as well.
My standards for answers are much higher than for questions. Someone asking a question is expected to not know stuff - eg, how to clarify their question so others feel more confident answering it. Before posting an answer, I try to do enough research to satisfy myself that the answer is reasonably accurate, comprehensive, and authoritative. As this takes time, I often won't commit to doing that if there is no interest from the OP.
A few times it has been suggested that I can copy my comment to an answer unmodified, which would improve our site stats, but not necessarily provide a quality answer, so I am reluctant to just do that. Having said that, I would not be the least bit offended by anyone who wants to copy my answer - this is a public forum after all, I provide answers for everyone else's benefit, not just my own.
There is already a lot of discussion on Meta about "Garbage Valley", which includes cases where someone posts an ambiguous, vague, or broad question, or one that is so simple that we wonder if we understood it correctly, and then the poster apparently disappears, leaving behind an unedited question, and losing general interest in the post. I don't see any problem with closing such questions.