Usually it is noted in listing requirements if personal comments are necessary.
Commercial waymarks, especially the subjective ones like Recommended Accomodations, really need a personal account. A restaurant or wine review is also nice to see in the those kinds of waymarks.
The only non-commercial category that I can think of that requires personal commentary is the Holocaust category.
Normally, it is up to the poster. I am a technical writer by profession, so I am usually just offering the facts. However there are those occassions where I need to share my experiences at the waymark. My Martello Tower submission is one example where I got the history of the tower from an elderly gentleman just passing by while walking his dog.