Whenever I try to put the comment $ $$ $$ $$ $$ $ on a site that supports LATEX, it results in an empty comment. And it succeeds! Try it for yourself (I don't encourage spamming, delete the comment afterwards). Mathematics.SE and Puzzling.SE are examples. Codegolf.SE is not an example, as it does...
MathJax/(La/Xe)TeX help
MathJax/(La/Xe)TeX help