The Symbol font was probably discontinued on the board because it’s discontinued in most modern browsers, and leaving it available on the board would just encourage people to use something that probably won’t be understood. Personally, while I understand why it’s fallen out of favor, I find it quite annoying that none of the “better” alternatives that we’re supposed to use now are as easy to use.
Greasemonkey is Firefox only, so no go for those of us who use Chrome.
Thanks, everyone! I really learned a lot 
you’re all intelligent and helpful.
I feel like that in threads talking about digital stuff…
Maybe there’s a thread topic in there somewhere…
squared.
-D/a
Dude, you’re being a total square.
Math ALT codes are your friends!
(¼ × √4 ÷ ¾)² = 0.444… 
BTW everybody, the π symbol is ALT+227 (remember you have to use the keypad numbers & specified leading zeros)…
From what I can tell, it’s not actually discontinued on this board. It’s just that no browsers display it anymore. The symbol tag still works, it just won’t use the [symbol]symbol[/symbol] font.
EDIT: Except in Internet Explorer.
There’s a GreaseMonkey script for this called TeX the World, and someone has ported it to Chrome/Chromium as well. That link says the original author isn’t maintaining it any more; I’m not sure if anyone else is. (The way it works is that people have set up web servers where you can send a LaTeX expression and get an image back; the script just replaces LaTeX expressions within [;…;] with image tags pointing to one of those servers.)
Edit: This is of course all done client-side, so people without it installed won’t see the images. The same thing can be done client-side. There’s a jsMath library which does this; the xkcd forums, for example, has it installed.
When square back, square pi.
I saw what you did there! Well played, signore or signora.