Would you kindly do the willingly and explain how? :)

You mean do the needful?

Maybe add </s> next time, although the smiley should have been a dead giveaway.

It's pretty easy, but also pretty rough - if you're good, you can certainly distinguish between an American, a British or an Indian English-speaking person writing.

I could be missing the mark here, but I'm pretty sure you were replying to satire. Based on the grammar used and smiley face.

Explaining the human brain's ability to pattern match will take more than a few sentences.

But whether someone is a native speaker is a trait that someone can legally and rightfully discriminate over. It's perfectly reasonable to reject someone if you think their English skills aren't sufficiently good. It's not reasonable or legal to reject them just because they were born in a different country.