The Lua reference manual is huge and subsequently not all that easy to navigate. The JSDuck documentation for MediaWiki's JavaScript is much easier to navigate imo, as is the other generated documentation. It also brings the added benefit of not having to maintain the documentation as well as the codebase.

LuaDoc will generate XHTML, but I've no idea what format is used for the current documentation.

A possible issue is producing documentation for the standard libraries as well as those added by scribunto as well as libraries that are written in php instead of lua.