You are missing the point here. The issue with the diode is this: With it IN the circuit, as designed, you cannot use the peak detecting chargers unless you disable the diode (by shorting it out). The diode prevents reverse current (which is exactly what is happening when the peak detector trys to sample the battery, the current goes in the direction it was not intended to go.. IN THE CHARGING PATH. There are several diagrams and descriptions available to do just that. The only problem is that if it is done, the warranty is usually void because of unauthorized modifications. By shorting the diode out, you can then use the peak detection chargers with the battery in the radio.

The 'reversing polarity' point is if someone accidentally puts a battery in backwards, the diode protects the radio.

The radio people (Futaba, Airtronics, JR, and so on) couldn't care less what kind of charger you are going to use as long as it's theirs, the one they supply with the radio.. and they don't particularly want you removing the battery just for charging. Think about it. They are protecting themselves with this diode. You can 'remove' it (not take it out, but short it out) or you can leave it alone. Shorting it out gives you the capbility to charge with peak detecting chargers. Leaving it in.. well, no peak detecting chargers, but you have accidental battery reverse connection protection.