I can only speak from experience with guitar noise gates.
Whenever the thresh-hold is set too high it will start to silence the signal before it needs to
Have you asked your question over at the Cockos Reaper forum?
With the quality of the interfaces and the digital recording software now days, I think it's better to solve this problem at the sound source, instead of trying to solve it after the sound is recorded. If the problem is gating a voice thru a mic, just record the voice then in the software manually edit out the offending parts where you would want to put a gate. If it's a guitar, buy a Boss NS2 or a Rocktron Hush noise suppressor pedal so you dont need to gate after its recorded. I gate my sources before they get recorded, anything else I edit manually in the software with mutes and volume envelopes. End result is none of my recordings/mixes have any gates in them at all. Leaves more CPU power for other effects.