Being hoisted by your petard is a well-known phrase from Hamlet by William Shakespeare, indicating an ironic reversal, or poetic justice. [1] Yet, it is somewhat of an ironic reversal [2] for you to write that the saying isn't apt.
The literal meaning of the phrase is that when your own bomb's explosion blows you backwards that leads to the derivative understanding of having experienced an ironic reversal or poetic justice in whatever situation is being experienced.
In todays world we now have the culturally apropos Petard Clothes for custom hoisting. [3] So, we actually have a double entendre [4] that should tell us all not to get hoisted by our own petards when telling HN posters not to wear their bombs.
[1] https://en.wikipedia.org/wiki/Hoist_with_his_own_petard
[2] http://changingminds.org/explanations/theories/ironic_revers...