I literally posted the exact opposite thing, here it is:

The phrase “I could care less” makes more sense than “I couldn’t care less.” They’re both idioms and therefore are both considered correct linguistically speaking.

But “I could care less” indicates you would prefer to not have to care about a subject so is expressing that you’d prefer to stop talking about it.

“I couldn’t care less” doesn’t indicate the current level of caring so you might say “there isn’t anything in the world that will make me stop caring about my children; I couldn’t care less about my children.” Without the idiom those aren’t contradictory. It’s only because of the idiom there’s an assumption the reason the person can’t care less is because they don’t care at all. But nothing about the phrase indicates this.

The level of concern for something with the phrase “I could care less” is indicated by context and the phrase indicates whatever someone may have assumed about one’s concern from the context is actually more than the person actual concern for it.

But people will often say “I couldn’t care less” is better than “I could care less”. They’re wrong and I could care less about their wrong opinions on idioms.