"could care less" is a mistake that just grew popular enough to become common use; it doesn't make any sense as a statement since it implies that you haven't hit your care 'floor'.

This may be a bitter pill to swallow, but silly and meaningless idioms are a dime a dozen. When push comes to shove, it's not something worth losing your cool over.

Perhaps they're a dime-a-dozen because they go unchallenged?

I've had junior members of staff express genuine surprise when I've corrected such mistakes in documents. It's a difficult thing to do without offense, but when clear meaning is imperative there's no leeway for doubt.

In 20 years time, will people still understand today's silly idioms or try to read them literally? "Nip it in the butt!"

Idioms survive hundreds of years once established and using them is not a mistake. "Head over heels" is another good example.

Don't worry, I wasn't mashing my fingers into my keyboard in a sweaty rage while typing the above. Life is full of little annoyances, some are fun to comment on though.

Mistake according to what standard?

That standard can't be "doesn't make sense", as a lot of language doesn't make sense

It was "As if I could care less" which is "couldn't care less"