There's currently no "move/copy" gutter on unified diffs, and the gutter does not have an aural cue (like "Line 15-25 were copied from X.c") for screen readers. The gutter should be available on unified diffs, and both the unified and 2-up gutters should have aural cues (although the unified mode is likely far more useful for users who use screen readers).
See PHI1877. The coverage gutter isn't part of 1-up diffs.
See PHI1877. When toggling diff display modes, the inline comment count in the UI header can lose sync with the page (comments removed when the old changeset is replaced are not subtracted from the count).