Take a look at this question.
I submitted an answer. Shalom then submitted an interesting, relevant, additional point, that was meant to enhance my answer.
Someone commented that his answer was not an answer at all, and that what he wrote belonged in the comment section to my answer.
This is only the latest example. Often times, many of us will agree on an answer given, and want to add additional information to enhance that point.
I view this as more significant than a comment, but not quite enough to be its own answer.
Would it be possible to create some kind of "sub-answer" functionality?
Alternatively, should someone who wants to add an additional point, simply edit the existing answer, and insert their point at the bottom?