a-b = c d-e = f c = f, providing (c,f !=0) When someone says: "It's A." and someone else says "It's B." and then person 1 says: "Same difference." is just plain dumb. If you say "same difference", then you must have compared TWO things, then TWO separate things, and take the difference of the comparisons. There can't be a "same difference" when there are only two things.
Slang vernacular is viral. It wends its way through the culture and the language, unimpeded by rules or common sense. Nevertheless, they manage to communicate (if only loosely) their meanings, generally speaking anyway. Thus, they 'catch on' somehow and both spread throughout the language and degrade it at the same time. 'I know, right?' is simply an example of a nonsense phrase which has wormed its way into the language, and chances are, it will pass, going the same dead route that now-stale phrase such as 'Totally!', 'Righteous!' and 'No way! Way!', and others. Out of curiosity, Faos, (and believe me when I say that I do not mean anything bad by the question) is English not your first language? I myself have always had a very hard time with other languages, because it's often very difficult to discern when a phrase is meant to be taken literally, and when it's just 'nonsense vernacular slang' like the phrase which irritates you so much.
Poster A: I hate Swoly-D's posts because he uses too many smilies. Poster B: I hate Swoly-D's posts because he always has to come up with stupid answers to posts where people are venting. Same (both posters hate Swoly-D posts) difference (different reasons).
I say it in the same vein as "you said it" or "you can say that again" or "you got that right". If I wanted to dismiss what someone was saying, I would just say "whatever". Personally, I find that offensive, so I don't ever really use it.
There are three versions that I am aware of: 1. "Right?" 2. "I know, right?" 3" "Yeah, I know, right?"