If you browse to to a commit in diffusion and click `View Options` -> `Show Raw File (Right)` it sometimes displays the contents and sometimes jumps to a temporary file which you then have to download to view.
Consider the difference between the following to files from the same commit:
https://secure.phabricator.com/rPc4dfc097c8c979b557c6f16a641c7544e43525b8#bc342b5e
https://secure.phabricator.com/rPc4dfc097c8c979b557c6f16a641c7544e43525b8#a176644f
This might exist in differential too, unsure.