I had copied this Emacs macro just for doing that. ;; one sentence per line (defun wrap-at-sentences () "Fills the current paragraph, but starts each sentence on a new line." (interactive) (save-excursion ;; Select the entire paragraph. (mark-paragraph) ;; Move to the start of the paragraph. (goto-char (region-beginning)) ;; Record the location of the end of the paragraph. (setq end-of-paragraph (region-end)) ;; Wrap…
You need to have a empty line between each line on HN for it to format correctly. If you also ident it by four space, it gets marked as code in the markup.