Comment by periblepsis on How can this Clapp JFET oscillate when its gate is tied to ground at the resonance frequency?

No, L1 and C2 have about 1414 Ohms each at the indicated frequency. Where did you get the idea that their impedance is zero? It's just at a minimum with the impedance of L1 and the impedance of C2 exactly the same value. But that minimum, nor their separate impedances, is not zero.