"Now try the question again, in what function or macro is the highlighted line located in? Was it easier to answer this time?"

No, not really, no. I didn't find it any easier either way.

I also don't buy this fellow's argument that lisp is the only language in which people rely on the editor to help them figure the the scope of expressions. I know that I use the editor when coding in C like languages as well. So I don't think that this argument for trailing parenthesis bears any weight.

The only argument that does make sense to me is that inserting a new expression at the end of a form can be annoying with editors that expect to operate on lines.

Personally, I find "parenthesis stacking" to look nicer, and it certainly has the advantage of being standardized and widely accepted in the Lisp community. One of the advantages of Lisp's syntax is that indentation and formating is so well standardized you can rely on an editor to do it right every time.