The Legendary Dragon Alephwyr, named Alephwyr, BA

Schools put people with the worst intellectual disabilities in institutions; one step up, they go to regular schools, but they're kept in little special rooms, away from other kids. Either way, normies don't know them.

I don't see what your anecdote has to do with his claims other than "the intelluctually disabled exist".

Perhaps because of your low IQ

Can you actually explain his point instead of just insulting me?

Yes. He is saying that because he has experience with low IQ people, he can confirm the accusations he is quoting. Others cannot because they don't have that experience. It's basically an appeal to authority of sorts, but probably a non fallacious one or a heuristically valid one

"I met people who I, from my subjective experience, felt had some of the qualities this other post claims low IQ people have" proves very little. The post he's responding is filled with claims about specific IQ cutoffs for abilities, which seems impossible to prove from anecdotes

To prove, yes. But it still provides evidence, just not evidence as powerful as scientific evidence. It's still enough to alter priors.

It provides evidence so flimsy as to be meaningless.