Click here to see whole article.
Below is the part of the article that mentions Kurt's guitar;
"When Nirvana was playing one of their first Boston gigs, Kurt Cobain came to me with a broken neck of a Fender Mustang, which was thought of as a smaller, student guitar. But he got a great sound out of it, and because he played it, lots of people had to have one because they wanted to sound like him."
Interestingly enough, the 7/15/89 Nirvana gig in Jamaica Plain, MA (Green State Station) near Boston Kurt did not play guitar because his was smashed and not operable. I'm assuming that the guitar mentioned in the article is the guitar that was eventually traded and recently sold.
Notice that the gentleman doesn't actually say he fixed the broken neck. Chances are Kurt couldn't afford and/or didn't have time to fix the neck.
Thanks to Rob from livenirvana.com for sharing this.