reportedly some banks track minimum payments. there's no telling how many of these and in what combination with other factors can lead to adverse action.
wamu cc website for example shows a check box listing your last three payments were either the minimum, above it, or below it. i would be surprised if amex wasn't also keeping a close watch.
I doubt that anyone knows this for a fact. And there's so much drama going on about AmEx, you could get any sort of response.
I suppose my attitude would be that if I could pay over the minimum, even if only $20, I'd go with that. Possible short-term discomfort, due to less cash available for other things, but long-term bennies of owing that much less.
This is a revolver you're asking about, right? Not a charge card?
Yah, it's Delta