There's a lot of interesting thoughts packed into this overview of UX Fest 2021, but the bits that really hit home were Jeremy's musings on A/B testing and dark patterns, particularly how one can feed into the other.
Using A/B tests alone is like using a loaded weapon without supervision. They only tell you what people do. And again, the solution is to make sure you’re also doing qualitative research—that’s how you find out why people are doing what they do.
Now, I suspect that if you were to A/B test a deceptive dark pattern, the test would validate its use (at least in the short term).