How do I get Emacs to fill sentences, but not paragraphs?

Question

I\'ve seen at least two recommendations on StackOverflow to insert newlines between sentences when editing LaTeX documents. The reason being that the practice facilitates so

Answer 1

I wrote the following which loops over a region and inserts newlines. Instead of using forward-sentence which didn't work for me, I use re-search-forward "[.?!][]\"')}]*\\( \\)", which finds all sentences followed only by two spaces (the regexp is a modified sentence-end). The newline is made using newline-and-indent.

(defun fill-sentences-in-paragraph ()
  "Put a newline at the end of each sentence in paragraph."
  (interactive)
  (save-excursion
    (mark-paragraph)
    (call-interactively 'fill-sentences-in-region)))

(defun fill-sentences-in-region (start end)
  "Put a newline at the end of each sentence in region."
  (interactive "*r")
  (call-interactively 'unfill-region)
  (save-excursion
    (goto-char start)
    (while (re-search-forward "[.?!][]\"')}]*\\(  \\)" end t)
      (newline-and-indent))))

To be able to fix improperly formatted text such as the example "chat chat chat...", fill-sentences-in-region first calls unfill-region which gets rid of sentence-breaking whitespace:

   (defun unfill-region (beg end)
      "Unfill the region, joining text paragraphs into a
       single logical line.  This is useful, e.g., for use
       with 'visual-line-mode'."
      (interactive "*r")
      (let ((fill-column (point-max)))
        (fill-region beg end)))

I use visual-line-mode and replace my default paragraph fill M-q to fill-sentences-in-paragraph with (global-set-key "\M-q" 'fill-sentences-in-paragraph).