  We discuss semiclassical Nariai black holes in the framework of
$f(T)$-gravity. For a diagonal choice of tetrades, stable Nariai metrics can be
found, emitting Bekenstein-Hawking radiation in semiclassical limit. However,
for a non-diagonal choice of tetrades, evaporation and antievaporation
instabilities are turned on. In turn, this causes a back-reaction effect
suppressing the Bekenstein-Hawking radiation. In particular, evaporation
instabilities produce a new radiation -- different by Bekenstein-Hawking
emission -- non-violating unitarity in particle physics sector.
