Deep Stall
From an aerodynamics perspectiive a deep stall is not confined to T-tail aeroplanes. It applies where an aircraft is not recovered in good time from the initial symptoms (heavy buffet, nose drop (longitudinally stable machines), sink, possible wing drop). A deep stall can be quite stable as DP Davies explains and requires extremely persistent and large AoA reduction.
Yes of course the T tail has the disadvantage of loss of elevator authority due to the change in wake from the stalled wing but that is more a case of a "locked in" condition. And most pilots think deep stalls only apply to Javelins, DC9s etc...