there is absolutely no specification. one who thinks there is has no idea what such words actually mean. thousands have burned their brains on this question
Its good they cancelled this thread. In fact I read the post, which shows you are completely ignorant of the history of markdowns and the various basically scientific problems they have posed. Thus e.g. commonmark, the basis of gfm, was devised in consortium between github, pandoc (whose author composed the specification) and assorted other well known markdowns.