When the phrase I know is used in English [ ], it signifies assent and acceptance of the point of view of a conversational partner. Its a fairly confident assertion of acknowledgement, of agreement.
On the other hand, the questioning right? stuck onto the end of a sentence is a request of affirmation of an assertion and a simultaneous invitation to disagreement. Right? Dont you think so? Do you agree with me?
So when a young speaker (and Ive only heard this phrase used by speakers under the age of 25) combines the two, it seems to be a simultaneous assertion of confidence and an instant pulling back of that confidence so as not to seem too pushy. It seems to ask for a continuation of the conversation. If the interlocutors continue the conversation, it may branch into areas of disagreement, but so far they are of the same mind.
Thank you....I think ;-)
Your explanation does suggest a certain mushiness in the phrase itself, and on the part of those who mindlessly repeat these things - usually after hearing them in some pop-culture context.
Everything gets started somewhere, and it’s an interesting study. From my generation: when did girls start saying that a young man was “cute”; when did we start calling things “cool”; where did “nifty” come from?
Words and fashions in language are fascinating.
JT -