Well, it _is_ (La)TeX syntax. With the exception that there, if you want a dollar sign, you have to type \$. But yeah, the syntax isn't made for Markdown.
I think the problem is the change. You didn't need \$ before, and now people's files are broken.
GitHub could have run their parser on a sample of existing Markdown file and check that the output doesn't change. They have such a huge corpus, with author date info, it is so easy to test that files authored before the feature don't trigger the feature.
GitHub could have run their parser on a sample of existing Markdown file and check that the output doesn't change. They have such a huge corpus, with author date info, it is so easy to test that files authored before the feature don't trigger the feature.