For my own answers I could, from 50 rep onwards, make such a transition myself: delete my answer and post a new comment. But who is able to do this for other users's answers? Is there a function for direct transformation? What is the recommended action if I think this should be done, but do not have enough reputation to do it myself - flag the answer for moderator attention? And will the user in question get a message for explanation? I mean - it could be a bit puzzling to learn "Thank you for A, but you should have done B, which however you are not allowed to do, so we did it for you."
Whenever we see an answer which is wrong, misleading, just a copy of an existing answer, or not an answer at all, we have the option to:
- edit it to improve it.
- downvote it. (requires 125 reputation on a beta site)
- vote to delete it. (requires downvotes and 4k reputation on beta sites)
- Flag it for moderator attention for deletion or conversion to a comment.
It happens quite often that unregistered or low rep users who are not able to comment everywhere (>50 rep.) post a comment or a question as an answer. These posts will be deleted or converted to a comment on request, or after we had received a moderator flag.
Sometimes a system-wide robot (Community Moderator) will cast a flag on low qualtiy post which then will put them in the review queue for us to decide further actions.
Sometimes such posts will not add any value to a question. These posts may be deleted without conversion to a comment. In the example you mentioned this could be debated, as we already have an accepted answer saying the same.