You might not be aware that the idom "I could care less" is in common usage, espechally in American english, and has the same meaning as "I could not care less".
Interesting. Certainly not in my country at least (and possibly most places English is spoken outside the US), it's a mistake that you will be pulled up for and possibly will harm your argument by making you look uneducated, since it's such a simple statement to parse.
Yes, either phrase is usually understood by American readers. However, "I could care less" has a literal meaning opposite from its idiomatic meaning and is likely more troublesome for non-native or non-American readers.
Also, when many people read "I could care less", they assume the writer has a deficiency in their education and/or attention to detail. Seldom is it advantageous to write "I could care less" instead of "I couldn't care less".
