This And Other Tips
Circa, I see you've been advised by ThePrimordialOrderedPair on superscript (none).
Tags are italics, bold, underline, and strikethrough only.
This and other tips in the unauthorized, unofficial, still-needs-updating AoSHQ Commenter's Survival Guide.
http://bit.ly/aoshq-csg
As for forming all those characters Pixy chokes on, I usually use this:
http://www.danshort.com/HTMLentities/index.php
Those without ampersands - you're just stuck.