I am medically handicapped and was also suicidal throughout high school. I had better test scores in high school than grades. I missed a lot of school and often failed to do homework.
In most cases, past grades are a better predictor of future grades than test scores. But college was physically easier for me because I had more control over my schedule and was thus better able to accommodate my handicap. So my grades went up substantially, more in line with my high test scores.
My health issues have long been a barrier to achievement. So this always gives me pause when trying to judge ability of other people. Maybe their poor performance says more about racism, sexism, an abusive childhood etc etc than it does about supposed innate ability. Maybe their good performance says more about getting social support, being born into the right family, etc than it says about innate ability.
But I will note that the comment you replied to said nothing about IQ. I only spoke of a need for validation and that's it. I was quite careful to not suggest it had anything to do with intelligence or competence.
I have spent quite a lot of my life failing to have a real career, failing to get taken seriously and failing to make much in the way of money. So there are ways in which I hunger for validation, yet Mensa does not appeal to me. I see it as mostly massaging one's ego and I would rather find actual solutions to my problems instead. Getting a serious career and adequate income etc will take my pain away. Validation from Mensa would be sort of like a painkiller, not a means to heal what ails my psyche.
I am not interested in remaining a loser but getting adorned with some sort of phony crown implying that I am totes not a loser, really. Instead, I want to stop losing at life, even if no one else notices.