Family Ties - S1-E22
John: Hey, D'Argo. How come I'm not afraid?
D'Argo: Fear accompanies the possibility of death. Calm shepherds its certainty.
John: I love hanging with you, man. My Dad's good luck charm.
D'Argo: Does it work?
John: I'm alive. So far. Kirk and Spock. Abbott and Costello. First base.
Chosen answer: It's never explained. John mentions a theory that his less technologically developed craft simply interferes with the wormhole less than the "superior" Vipers, but they never make a concrete determination on that point. But we also have to take into account the fact that Moya traverses wormholes with no ill effect as well.
Garlonuss ★