Topic on Extension talk:Scribunto

{{{{FULLPAGENAME}}}} as the first argument is interpreted as a literal string.

You don't need to pass it. Lua already has that information, see Extension:Scribunto/Lua reference manual#frame:getTitle. If you really want to pass it anyway, you can use Extension:Scribunto/Lua reference manual#frame:preprocess .

{{{{FULLPAGENAME}}}} is interpreted as { {{{FULLPAGENAME}}} }, not {{ {{FULLPAGENAME}} }}. Since there's probably no variable named "FULLPAGENAME" being passed it, it seems like nothing happens. You could add those spaces if you really want to do it.

But that seems like a rather odd thing to do, unless you're doing it inside a <noinclude> or the like.