I once saw a demonstration on how much strength a webbed strap loses when twisted. It was quite surprising how much one little twist lowered the strength. It wasn't a seatbelt, but I'm sure the concept still applies.
Without going out to look at mine, couldn't you just untwist the webbing by working it around (pinching, bunching, twisting) where it slips through the "key?" Maybe not, but that's all I can think of short of replacing the whole thing. I don't know how he would've gotten a new key part on there without un-stitching something, and if that's what he did, I wouldn't want to rely on it anymore.
As for not wearing one... I had a good friend who decided he didn't need to wear one to drive across town.... Keyword there being, "had."