Content of Turtle and RDFa documents should be wholly and entirely preserved

Originally discussed by @RubenVerborgh, @kjetilk, and @TallTed in https://github.com/solid/specification/issues/301#issuecomment-955206910 and preceding

[@TallTed] I am rather weary of explaining this over and over, and hearing back, "we don't care about your idea of what data is."

[@RubenVerborgh] I do care about your idea; but we need some pointers to back that up.
And insights into the consequences of adopting that viewpoint versus another; I see many thing we'd not be able to do, not really gains. I don't know any sources that consider RDF whitespace and comments to be data.

If they need to be data, then the MIME type should not be RDF, but rather text/plain or similar (or maybe even better application/octet-stream to avoid encoding issues), and then data will be preserved.

[@TallTed] then non-RDF contents of Turtle and RDFa files MUST be preserved and these files MUST be treated as ldp:NonRDFSource.

[@RubenVerborgh] A citation would be helpful.

My understanding of the matter is that a content type determines what transformations are allowed with preservation of semantics. This is not unique to RDF at all. Minified JSON carries the same meaning as the unminified version.

(@TallTed Should you want to continue the discussion, could you please open another issue as per @kjetilk's suggestion?)

Start with the linked discussion in specification issue #301 and the quoted positions in this issue. Determine whether the specification needs a normative change concerning preservation of non-RDF content and treatment as ldp:NonRDFSource; done requires an agreed resolution and corresponding specification text.