The problem with adding so much complexity to the parser is that it's now impossible to predict how any given Markdown is going to render on Github. If Github's parser was open-source, you could at least look at the source to figure out this stuff is handled, but it isn't, so the only alternative is tedious experimentation.

One of the main draws of Markdown was that it was so simple you were rarely left guessing how any given input would be handled (though the lack of standardization hampered that).

It’s simplicity is also it’s crutch. It lacks so many niche things (like math) that every implementation have their own syntax.

The problem with heuristic parsers is that you can't learn the rules, so the only way to use it now is with live preview.

Author here.

One problems is that the parser doesn't work harder yet, and it will be difficult even for GitHub to make it so. The $-syntax is familiar to TeXies indeed, but if the cost is that math won't ever work properly, I'd rather have a markdowny syntax.