Hi, CK. Thanks for your explanation. It looks like you left out a word or something in your edit summary; anyway, I didn't get it.
I considered your explanation and looked at the article (left it, looked again, left it, ...) and I have come to the conclusion that the certs listing as you've changed them just look too much like a random order. The alpha-by-provider is neater, in my view, than the provider-in-order-of-country-where-we-have-one. Maybe your way would look better if we always had 10 charts and 10 certs, and they'd sort of match up. Not sure.
In any case, if you feel strongly about your preference on Katy Perry discography, I'd guess you'll want that system on every article, yes? In that case (especially), it would be great if you would (re-)start a discussion of the sorting of the certs over at WT:DISCOGSTYLE. There, you'd have a chance of building consensus one way or the other (it was most recently for alpha-by -provider, but concensus can change, and it's a smallish group there). We'd expend less energy on reversions and explanations then. Thanks again for your explanation. —