"I'm not happy with that solution, however, because it ends up throwing away the associated comment-votes"
Good! You should be happy, you are doing the question (and Academia) a favour!
Answers as comments are damaging to SE because they circumvent the quality assurance mechanisms put in place by SE.
- The community can’t down vote a comment.
- The community can’t edit a comment.
- A comment doesn’t move up and down based on votes (i.e good ones to the top, bad ones to the bottom).
- A comment can’t be marked as the accepted answer.
- A comment doesn’t show a question as having an answer.
- The moderation options for dealing with a comment aren't the same as the moderation options for dealing with a comment (including review queues and the like).
All those up-votes you see could just as feasibly be outnumbered by double, triple, octuple, even more! down-votes had the answer-as-a-comment been made as it should have been: as an answer.
The users of Academia do seem to do this a lot, even the high rep members, so it is nice of you to prod people into moving them into answers first. If you don’t mind coming back to the question again then by all means leave a ‘grace period’ between prodding and flagging but if you don’t want to then just flag with a custom moderator flag of ‘Answer in comments’ and the mods will normally clear out the comments and leave a reminder message of what comments are for. After having a handful of "good" answers-as-comments deleted users generally stop doing so.
You could even add a link to the page for the comment privledge into your proddding comment to help remind users what comments are for: https://academia.stackexchange.com/help/privileges/comment
Here are a couple of the key points from that page (some emphasis mine):
When should I comment?
You should submit a comment if you want to:
- Request clarification from the author;
- Leave constructive criticism that guides the author in improving the post;
- Add relevant but minor or transient information to a post (e.g. a link to a related question, or an alert to the author that the question has been updated).
When shouldn't I comment?
Comments are not recommended for any of the following:
- Answering a question or providing an alternate solution to an existing answer; instead, post an actual answer (or edit to expand an existing one);