The thing that first comes to mind is recently realizing that even I was infected by a dangerous memeplex directly decended from christianity.
I've always been an atheist and wondered what it was like to realize that there is no god, or what it's like to strongly believe some obviously false thing just because it's what people you grew up with believed. I remember thinking "well, I'm right on the big things like god and psychic powers and such, I guess epistemic rationality is a solved problem"
Now I'm like "holy crap, I (we) really suck at this, and could be way better".
NOt sure if this is what you're looking for.
Not saying which it is is pretty obnoxious, but I'll have to assume you've been bitten by the moldbug
Information that surprises you is interesting as it exposes where you have been miscalibrated, and allows you to correct for that.
I suspect the users of LessWrong have fairly similar beliefs, so it is probable that information that has surprised you would surprise others here, so it would be useful for them if you shared them.
Example: In a discussion with a friend recently I realised I had massively miscalibrated on the percentage of the UK population who shared my beliefs on certain subjects, in general the population was far more conservative than I had expected.
In retrospect I was assuming my own personal experience was more representative than it was, even when attempting to correct for that.