[mnot]

Making breaking changes to markdown is about as practical as doing it to HTML -- already existing content and mindshare give the current form massive inertia.

The is especially the case when it works for the vast majority of use cases (or can be hammered into them); ambigiuities are very visible to implementers and detail-oriented folks, but most people never see these issues, or don't care about them.

And, while it sucks that it's complicated to implement, that burden is on relatively few people. See also: the HTML Priority of Constituencies.