Discussion Forum—A Way with Words, a fun radio show and podcast about language

In this morning's NPR news a segment on the life and work of composer Steve Reisch contained this comment, "His work was really sorta extraordinary." The juxtaposition of the adverb really with what for me is a phrase that waters down the effect of a nominal, sorta, and the strong adjective extraordinary caught my ear. Sorta seemed to cancel out the adverb really and to reduce the strength of the meaning of extraordinary. My reaction reminded me of discussion of the frequent use of the phrases sorta and kinda by speakers of American English. I remember hearing broadcasts of comments from Brits and other people who don't speak American English. The commenters wondered aloud at the rationale and meaning of sorta or kinda in American English. A few of them felt it was unnecessary. Some of them thought the use diminished the clarity or impact of statements. I seek your wisdom: What is the linguistic term for this kind of usage, and what do linguists say are the origins and meanings of the phrases?

Thanks very much!