@xahteiwi emacs's markdown-mode partially renders markdown so pesky in-sentence markups are gone... then setting a high enough fill-width unbreaks the paragraph into a single wrapped line. then select the line, replace ". " to ". LF" and you would have the desired formatting. record a macro of the above and repeat over the paragraphs until done. tried it in a small doc and it seemed to work mostly... code, lists, quote blocks are all skipped properly... because the markdown-mode doesn't render tables, those need to be skipped manually. of course if you don't use emacs, you now have two problems :) (apologies to jwz).