Back in the day....when all microwaves used WAVEGUIDES and diodes were in tall ceramic packages with pretty large package inductances....it was hard to get those packaged diodes to reflect signals when they were forward biased. Then some bright guy thought "Hey, could I use a coaxial bias network to add an effective series capacitance, reactive cancelling-out the package inductance, and get a near perfect short circuit across my waveguide? That would give me at least 35 db isolation per diode!". and that is what he did, he "tuned out" the package parasitics.
But, like anything matching out a reactive part, it had limited bandwidth. That is why today we use pin diodes with the absolute minimum package reactances, and no longer try to "tune them up".
You might still run into this in a high power waveguide switch...especially if it uses stacked pin diodes to handle high power.