Only two things really matter. Do you like your home and can you afford it? The rest is just paper gains/losses that only cause lost sleep if you let them

Sorry, but that’s completely wrong. Being underwater matters a lot, since you can’t sell your home and move, or use the equity to buy another home. Not being able to rent for more than your PITI also matters, since you can’t rent the home and (say) relocate temporarily for a year for work or just travel the world. Meaning that you have a whole lot of people who are “tied to the land.”

Unfortunately, mortgage writedowns mostly don’t allow for rental or resale at the written-down price, so you still end up with a stuck class of people.

Not good. The writedowns, if they happen, should be permanent to allow for mobility.