Is there a syntax-highlighting for LuaLaTeX on this site? I think it would be necessary to color the Lua commands in the LaTeX code, because Lua is a integral part of (Lua)LaTeX. I think it would improve the readability of code an maybe push the acceptance of Lua for use in LaTeX.
I have no idea about programming a syntax-highlighting, but the Lua code is always placed in \directlua{}
or \begin{luacode} ... \end{luacode}
(and some other environments). So I guess and hope it is not so difficult to create a highlighting. Additionally there could be a new button above the answer text field like the 'Code Sample' button, but for Lua commands (i.e. for placing just Lua code without LaTeX commands and Lua environments).