Here's an example of a new user doing the right thing, and looking to see whether their question has been asked before. However, it was unanswered, and their only option to bring attention to the question seems to be to do the wrong thing, and ask it again in the answers section.
I apologise if I'm missing something obvious.. how should a reviewer advise the new user? It seems unfair just to slap the post down.
"However, it was unanswered, and their only option to bring attention to the question seems to be to do the wrong thing, and ask it again"
The correct thing is to ask a new question. If a question is technically a duplicate but original has no answers, there is nothing wrong with asking it again.
Do so by making a new post (not a commenting or writing in the answer section), and ideally mentioning the original post with a link to it, so as to acknowledge it and show research efforts.
It is not consideres a duplicate nor a wrong action, and except for mods you can't even close vote as duplicate of a question with no answers, or if any answers only have no upvotes or negative score.
To answer your question directly, to bump an old question a user can:
That answer will end up in the Low Quality Posts review queue (because of its length, and because I flagged it as Not An Answer), where one of the options after 'Recommend Deletion' (or 'Delete') is to post this comment:
This does not really answer the question. If you have a different question, you can ask it by clicking Ask Question. You can also add a bounty to draw more attention to this question once you have enough reputation.
That post is not an answer, so it should be deleted, but the new answer did bump the question, so perhaps somebody stumbles upon it now and can contribute to a solution. That would be a nice side effect.
