It would also mean another Turing complete language embedded in browsers, in addition to… JavaScript, XSLT, GLSL (WebGL), WebAssembly, CSS itself if you squint, fonts, WebSQL (TIL some browsers still support it)… probably more I’m not thinking of.
> I do not encounter TeX users who write their own macros often.
But they use packages that they got off CTAN that were written by someone who is not at central office (not that there is a central office, but one would be needed if you stripped out the ability to write serious macros since there would have to be someone adding approved features).
Developers use macros. Now since they are developers, they had less problem develop with a programming language and may prefer to do so than using the TeX macro system. The alt-TeX can simply be extended with plugins or modules.
If you mean that SVG is Turing complete, I was thinking of it, but not having much experience with it, I'm not sure what exactly is Turing complete there (without XSLT, which I mentioned).
I guess one more wouldn’t hurt.