It's kinda ridiculous that we support 7 different identifiers for this formatter. It could cause problems if we ever introduce a built-in formatter that starts with s or n, as those letters are already taken up by this formatter.

What do you think about deprecating s, n, spec and nested in 2.99 and removing them in 3.0?  Then it'll just be d, doc and documentation we support which seems like a good and sufficient set.