Doing C-u C-x = on the character in the completion window shows (where
it's blanked out as expected)

    xft:-unknown-DejaVu Serif-normal-italic-normal-*-15-*-*-*-*-0-iso10646-1 (#xA6F)

whereas, the same character in other places shows (where it's not
entirely blanked out)

    xft:-unknown-Unifont-normal-normal-normal-*-15-*-*-*-d-0-iso10646-1 (#x2803)