Have you ever come across an example of a dually embedded content clause functioning as subject, such as
That that it works is obvious is disputed.
Linguistics Stack Exchange is a question and answer site for professional linguists and others with an interest in linguistic research and theory. It only takes a minute to sign up.Sign up to join this community
It turns out that this type of embedding is discussed (and marked with #: semantically or pragmatically anomalous) in Huddleston & Pullum's CGEL in the section called 'Processing factors', pp 1405-6. Also, Pullum tells me that such examples are never found. "Fred Householder asserted in a couple of book reviews in Language that English has a surface constraint forbidding "that that". Terry Langendoen's view is that it's a processing matter: stashing two subordinators in a row as promissory notes for finite clauses that are to come is too much of a strain on the old processing box."