When I bought a plane ticket and ticked the "Disability assistance - hard of hearing" box and then went on to seat selection, it offered to let my wife choose a seat (for a fee), but said that for me seat selection was "unavailable". When I went back and unticked the box, it offered to let us both choose a seat.
That seems odd. All I can think of is that maybe they didn't want me choosing an exit row, and went overboard? Why are deaf people not allowed to choose their seats?