Earlier quoted context omitted.
Sometimes I like to go on StackExchange, find questions I'm deeply knowledgeable in and where people are saying things like "it can't be done" and reply with a code example doing the thing.
I really don't understand how people can answer questions they are not 101% sure of the answer, on a public site like that. I mean, informal chat with a colleague? Sure. But to go on SO and do it, it's unthinkable for me.
My brain doesn't seem to index many examples of my own wrongness, even though I have more than once thought "this would be a good mistake to remember", and the worst that I can remember is under an NDA (very confident and very wrong), so the only example I can give is a currently ongoing personal error:
I've spent the last 5 years improving my German substantially, but the whole time I've been trying to estimate my current skill level and gotten the same answer, B1.