I must admit "I could care less" has never made much sense to me, but it only seems to be Americans who say this. In England we say, "I couldn't care less", which means just as it sounds. The quoted blog post sounds spot on to me, definition-wise.
One of the great things about language though, is that it's everyone's. So if someone wants to break grammatical rules, in spite of it making our ears and eyes bleed, so be it. As long as the meaning is clear, which I suppose it is whichever version you use. Despite the literal meaning of the words, people will know what is meant.
Language is plastic, by that I mean it changes and moulds with the times, so whilst we no longer write 'ye olde shoppe', one day instead of "I couldn't care less", may just be "I less." Hmm, that sounds a bit stupid, but you get my meaning. So the current argument of 'could' and 'couldn't' will be obsolete, it'll be something else instead.