Moderators have had the ability to convert an answer to a comment for some time now. In addition to converting an answer to a comment from the post itself, there's also a button that shows up in the moderator queue when an answer is flagged for certain reasons.
This is convenient when we can read the entire answer from the queue and plainly tell that it should have been a comment. The problem is that there are often more comments on the answer that also need to be moved, so I always feel the need to click through to the post and check it to be sure we're not losing any information. (This is often the case when the "answer" is asking for more information and the OP provides it in a comment.)
This button and the corresponding "convert to edit" button would be even more convenient if they only showed up when there were no comments on the post that's flagged. That way moderators would know that it's always safe to click the button from the moderator queue without needing to check the post for follow-up comments that need to be preserved.