The way I handle this is to parse them differently. They mean the same thing, but “I couldn’t care less” is sincere and “I could care less” is sarcastic.

Sort of like, “I suppose it’s possible that I could care less about that” reduced to the phrase.

Because both phrases obviously communicate the same meaning, a lack of care, the issue for me isn’t in the understanding but in the parsing. So I had to come up with a way to parse it as sarcasm so it doesn’t bother me.

Like when someone says, “I’ll try and be there” my brain, mildly traumatized by really good English teachers in my youth, screams, “YOU’LL TRY TO BE THERE.” But lately I’ve been making an effort to interpret the “and ” following “try” as an alternate form of the infinitive, since it’s so readily accepted and common in spoken English. We already construct other verbs that way anyway (eg. “I’ll go and do that”).

I…might have a touch of the ‘tism. It wouldn’t surprise me. 😅