'Big Brother' Austin & Liz -- Showmance Survives ... We're In Love

"Big Brother" stars Austin Matelson and Liz Nolan are shattering the taboo of reality show romance ... much to the dismay of a torrent of online haters.

Austin tells TMZ when Big Brother ended ... he was flooded with messages calling him a "disgusting cheater" and "classless" for breaking up with his then-GF on TV.

For the non-fans ... Austin and Liz kicked off a relationship early in the show ... despite the fact that Austin was a taken man.

They both got called out for the love triangle ... in one of the most awkward moments of the season.

Austin says, he and Liz are now exclusively dating, have met each other's families and Liz plans on moving from Miami to LA to be close to him.

Love is cool ... but $500k would have bought a lot of friends.