And I would be even more hestiant with 2 posts to ask a guy with 5000 posts what his background is. Maybe that is just me.
While I agree with the majority of your post... I've got to take issue with the logic here.
Raw numbers of posts don't necessarily mean much, on any message board. Sometimes, two members of a forum will get into a exchange that's better suited to email, and post 20 or more times in a day...but they're not really imparting information to anyone else. Or, there are always those people who have to add a comment, even if it amounts to "what he said!". On one forum that I participate in, many members feel it necessary to award reputation points & post when they do... Again -- that could inflate the numbers of posts.
On the other end of the equation, since this is a ninjutsu board... Hatsumi (forgive any errors of etiquette; they're unintentional) could i theory sign up tomorrow and start posting. Despite his acknowledged mastery and knowledge -- he'd have very few posts! Would that mean he's not credible?
The best advice (often in real life as well as message boards) is to assess a person's input based on what you see and what they say. I've made no secret in my very few posts on these particular threads (I post more in some of the more general areas) that I don't and never have trained in any of the current forms of ninjutsu/taijutsu; it's just something that I was once fascinated by. And I find the discussions here to be very interesting.