I've noticed (particularly on 3D Printing SE, but as I understand it this happens across many sites) a number of instances of new users wrongly posting an answer to an old question to bump it, asking if the OP ever found a solution.
This is of course a misuse of the answer workflow and gets deleted or converted to a comment by moderators, but the reason it's happening is because there's a genuine need for new users that's not being met.
They arrive at the site after searching for a solution to their problem, find a question that matches it, but for which there is no good answer, and they're unable to comment or interact in any other way because they don't have sufficient reputation.
In order to avoid this misuse of answers and the perpetual need for moderators to clean them up, and frustration from new users on the other side, could something be done to make a constructive workflow to meet their needs?
Maybe allowing users without comment privileges to post an account-lifetime-limited number (3?) of "prefab comments" along the lines of "I'm having this problem too. Did you ever find a solution?" This would avoid making it a vector for spam and low quality comments while allowing users to do what they're trying to do (which is something useful and legitimate) and giving them a better first experience with the site.
I noted in the comments that, when this kind of action prompts me to self-answer my own old questions I'd forgotten about, it's not actually the bump that matters, but the inbox notification. So perhaps a decent workflow would be something to express new interest to the author of a question with no accepted answer. But this only works if the OP is still around.
Allowing limited commenting would also facilitate other users seeing renewed interest in the question and taking a stab at answering it.