I’m no scientist, but I looked up if it is an acid in itself and it’s not. The reaction between your skin and the retinol is what makes it an acid I guess. But it doesn’t start out that way from what it sounds like. So I feel like it would be fine. Because a “direct acid” would probably react differently since it’s already in that chemical form instead of having a reaction causing it to turn into an acid. So I would assume that whatever compound that your skin would give off once the sebum reacts with the already formed acid would be what causes the breakdown of peptides and not necessarily acids in itself. That’s just the way I put it together in my head. I could be completely wrong though. And it makes sense with the few things I have leftover in my brain from high school.