A Twin Otter is not a jet.
Had a Boeing factory tour by a BCA test pilot. Asked him about tail de-icing. Like others have said - you don't need it. Flight test showed it had no effect and when it got large enough it came off.
That is not to say it's OK to take-off with ice. It is not. The flight test is about inflight. On the ground it is not acceptable to have ice on the tail prior to departure.