That's an impressive piece of dividing aspects of written language! So it appears your friend was able to separate the semantic aspect of reading entirely from grammar and mechanics. I know I can read a document only for the latter when the content is beyond me (I proofed my sib's doctoral dissertation in a field far removed from my own areas of expertise), but I'm not sure if, without setting out to do so, I could switch into that kind of proofing only mode if the content were readily accessible. I'm sure he had lots of practice. I can, however, read lengthy passages out loud with expression, without processing any of the content.
And I agree, it seems the same would be true of handwriting in some cases.
