Strange rant. From a user perspective, it is very handy to have a very simple text format in which you can occasionally insert complex mathematical expressions. And at the same time, it's perfectly okay for most implementations to NOT support this syntax

Ok

Feels like a weird hill to die on. I don't think I've had a single issue with single dollar signs being math block boundaries. It's also weird to say that Github is the one who invented this or that it was a malicious choice, when it's clearly MathJax, which is far from being "antiquated ugly crapware". It is still used by Wikipedia, most scientific websites, etc. Yes, KaTeX may have advantages, but MathJax is very much alive.

There is a myriad of different software which uses different math delimeters. Some markdown flavors for example use \(\), which is probably the worst of them to use. Is that also malicious?

A much better rant about math syntax in Markdown would be that all flavours still use the LaTeX syntax instead of the very obviously superior Typst one. If you think not embracing Katex instead of Mathjax early enough is a malicious choice, then is this one malicious as well?