Nope it doesn't even work as sarcastic since that would be "wow, they care so much".
"They could care less" means they care somewhat and so you're effectively saying that it's SOMEWHAT important to them which is a super lukewarm statement to make and quite pathetic.
By its nature sarcasm has to mean the opposite of what you intend to mean. By going for the middleground with what essentially means "somewhat interested", the sarcastic effect is nullified.
Nope it doesn't even work as sarcastic since that would be "wow, they care so much".
"They could care less" means they care somewhat and so you're effectively saying that it's SOMEWHAT important to them which is a super lukewarm statement to make and quite pathetic.
Yes, it completely works as sarcasm. This argument is stupid - and I mean that with complete sincerity.
By its nature sarcasm has to mean the opposite of what you intend to mean. By going for the middleground with what essentially means "somewhat interested", the sarcastic effect is nullified.