It's a way of designating a single thread for a particular hotel so that people don't keep creating multiple threads about the same property.
Can't say I've seen an "official" heading on a thread much except when it is coming from Hilton Honors representative and then we know it is the "official" Hilton word on something. When I saw this thread the first time, I thought the ESJ management had created a thread. Often you see in the Hilton forum a format where there is a thread for trip reports and reviews and sometimes one for questions. For example:
http://www.flyertalk.com/forum/hilto...t=conrad+tokyo
http://www.flyertalk.com/forum/hilto...t=conrad+tokyo