I would have to say that they don't read these message boards. Maybe someone that is curious may wonder onto a review board and then read a few, but the head offices don't use review boards on the internet to make decision and changes. At least not that I know of.
However, they do read the comment cards that are filled out by the passengers at the end of every cruise. Every single one that gets turned in does get read by someone. With the last cruise line I worked for we read comment cards every debark/embark day. The ones that were turned in that morning, then got read that evening. Every embarkation day at 7:00. It was boring but some of them would be hillarious. All the department heads other than the CD (they would send the ACD instead) would get together in a room and read the comment cards until every single one had been read. They get seperated into good, bad, and genereal piles and then sent to the Hotel Director from there. He reads what he wants and moves them on to the office. They also get copied and sent to the departments mentioned in them for recognition of individual crew members.