I have mixed experiences, I think more times than not they read them, but some do not read them at all, it is down to the individual, and maybe even what type of day they are having. Most of the time the comments appear to be read and honored

At one HI, where there is a very spread out layout I put on a request for a room near the lift (for OH as he could not walk too far at that point due to a health issue). I was allocated one of the rooms furthest away. When I asked it it was possible to be moved I was told I should have made a request to be near a lift, and when I said I had and she checked I got the comment that I should have phoned as they do not always read that part fo the booking. She also refused point blank to move me as it was apparently my fault. Needless to say, that is a hotel we will not be returning to.