I'm used to saying stupid things and coming under fire, instead of learning not to do it, I've learned to handle it instead. It's the Acme way!
But no, when I found out about the gearbox, my initial reaction was "quick, get rid of it before its noticeable!" but then Shauncr91 made me put myself in the shoes of the prospective buyer, and I don't think I could do that to someone. Even if they wouldn't know that I was aware of the issue.
I'm clearly a horrible person, but if I was selling a sub £1k car, unless I was aware of a serious issue which would likely cause a massive bill in the very near future, no way would I say anything. Bearings wear out on old cars and they make funny noises - in fact, I can't think of any cheap car I've driven/sat in that has sounded as it did when it left the factory. As I think I said before, my Astra had a bit of a whine in 5th when I sold it - several years on it's still running fine.
I suspect most people on this forum would do exactly the same thing, whether they'll admit it or not is another thing.