Looks like I can post mathematical notations here without glitch. I want to know all syntaxes for that. Is it documented? Is it all old Matlab?
The official list of macros supported by MathJax should tell you what macros you can use. It also has a link to examples of all macros created by Carol Fisher that should be very helpful in understanding how to use them. Carol's examples were written for v1.1, so there are a few items it doesn't document, but by-and-large it is pretty complete.