Other, "quick and dirty", solution:
.square_brackets:before { content:'\005B \005B'; } /* Square Brackets [[ */
.square_brackets:after { content:'\005D \005D'; } /* Square Brackets ]] */
.curly_brackets:before { content:'\007B \007B'; } /* Curly Brackets {{ */
.curly_brackets:after { content:'\007D \007D'; } /* Curly Brackets }} */
And for convenience in tiny.css_selectors:
Brackets [[ ]]=square_brackets;Brackets {{ }}=curly_brackets
More entities can be found here:
http://www.evotech.net/articles/testjsentities.html