I suspect moisture damage caused the liner to separate.

I first noticed a bubble under my driver sun visor that has now spread to the entire visor area. I fear that this is going to continue and at some point become a safety problem when the area gets bigger and might obstruct my vision while driving.

In all my years of owning Honda's, they head-liner was never a problem. This is just crappy workmanship, 7 years old and it should not be falling down. Professional fix ~ $200, or temporary 3M respray ~ $20 for the DIYer.