What is the coat film?

It is more reliable to put a capacitor in series with it. The friction and rubbing from plugging and unplugging will remove any film.

Seems like a cool trick, espassialy if you dont have to plug/unplug very often

Someone who tried this, how much insertion loss ?

I think you can not use at low frequencies...
For maybe higher frequencies..

I saw one product of one China Nanjing verdor. On pcb trace, there is a coat, then pin was soldered on, but DC is blocked, and I guess RF is shorted. I will measure later and let you know the results.

Thx, keep us updated

I tested it today. The pin is really RF shorted to GND and DC blocked, with DC=0.35V. I guess that they use some glue, who can suggest that?
And I simulate in HFSS about the epoxy of FR4, its insertion loss less than 0.1dB when epoxy thickness is 0.1mm.

I will remember that trick