It was more like a 10% success rate. I emailed roughly 10 schools that sent me solicitations (an already biased sample?) and received a positive response from 1. (This was a separate test with schools different from the 36 I asked application fee waivers from)

I think it would be helpful for everyone to know how this type of question is received by an adcom, but part of me feels like the adcoms will be obliged to answer a certain way when I ask them how they received it. In any case, I will ask, and will post the responses here.