I've enjoyed reading through this thread. I have heard some of these myths and others were brand new to me. I've thought of another one that my family has personally proven time and time again is false... well, at least for our cat. I realize all are different.
I've often heard that no cat is ever a good traveler and it's just not true in our case. Our cat has traveled on our road trips with us for nearly 10 years now. There's at least one trip every year that is around 1,000 miles each way. We have a huge carrier for her with cushioning, so the ride is comfortable. When we're ready to go, she just looks around for a while and then settles in to get comfortable. Never makes a sound and the "hum of the road" seems to comfort her.
I agree with the furniture scratching issue... we never had a problem with that either, although I'd been warned about it. We just keep a few cardboard "scratchies" around the house and the cat loves them and it satisfies her when it comes to needing to scratch.