Slightly O/T but still about flying machines
For gliders it is more than a fashion : since the Phönix (1959), 90% of plastic gliders have been designed with T-tails, notable exceptions being the Std-Libelle and pure aerobatic gliders (for structural reasons as mentionned by ft).
The determining pros are indeed the interaction with crops and the rudder authority in spins. Gliders are probably the most stall & spin prone airplanes (aerobatics excepted) as people tend to fly as slow as possible (min sink or even less) when cirling in thermals.
Never heard of deep stalls for gliders. (or seen anything in flight manuals). I guess the layout is not favourable (forward position of wings)