Given this as Module:Foo:
local p = {}

function p.main(frame)
return mw.html.create('span'):css('color', frame.args[1]):wikitext('Hello world')
end

return p

The following code will not produce the expected result:
{{#invoke:Foo|main|<nowiki>#00ff00</nowiki>}}

The color won't work because mw.html's cssEncode escapes the strip markers, preventing the parser from unstripping them.

Version: unspecified
Severity: normal