I'm looking for a minor mode to keep paragraphs filled at all times while typing (similar to what aggressive-indent-mode does for indentation). It also needs to be smart enough to only fill comments (and maybe strings depending on the language).
Some things that I've tried are:
auto-fill-mode automatically fills while you are typing new paragraphs but doesn't refill when you edit paragraphs.
refill-mode does constantly refill paragraphs but it tries to wrap code into paragraphs as well as comments.
I tried adding fill-paragraph to the after-change-functions hook but it screws up undo and plenty of other things (this is probably all fixable but would take some effort).
There are a couple of caveat's that I've stumbled across so far:
elisp-mode (possibly others) does some fancy code filling when you call fill-paragraph, this may or may not be what you want. Can probably be fixed with by testing if point is in a comment or docstring but I'm not sure how to do that.
You sometimes can't easily enter multiple spaces (because the fill-paragraph kills any trailing spaces). Since the space-bar now acts like just-one-space it's probably ok to replace that binding with (insert " ").
I made a minor-mode containing this functionality, it's available on github or in the melpa package aggressive-fill-paragraph.
org-mode, but you may try rebox2