In another lifetime(1960s) I experienced true elevator stall but it was caused by external influence on the aircraft. Part of the requirements for a fullscale commercial glider pilot ticket was a certain number of winch or auto tows.
We used 1100 ft of .120 single strand wire hooked to an automobile for the towing apparatus. When the maximum altitude was reached, the stick could be pulled back against the stop and the elevator would stall letting the nose down slightly below the horizon. When the stall occured the wing would be at very slight positive angle to the horizon. This was caused by the fact we used the nose release as the towing attachment as the old S-222 serial number 07 had no cg hitch.
Over the years I flew and instructed in a number of different aircraft type including some with stick shakers but the old 222 glider was the only situation where I experienced true stalling of the elevator and not the wing.
ORIGINAL: Bax
When a control surface actually stalls, it becomes ineffective. Because the pitching tendency of most conventional aircraft is nose-down, the stabilzer/elevator is used to produce a downforce on the tail. If the elevator stalled during a positive 'G' maneuver, then the model would pitch out. As was stated above, a loop's radius would increase, or the model might even quit looping and pitch the opposite way, outside.
Full-size aircraft have used a variety of devices on the horizontal stabilizer/elevator to help them. The Boeing 727 has vortex generators on the underside of the stabilizer to help keep flow attached when it's at high pitch in relation to its relative wind. This makes sure it won't stall during times when high control surface deflections are needed, such as during maximum performance low-speed flight and landing.