Whether or not they actively participate in discussions here, I do not know. But, I know of multiple individuals who play one role or another in the admissions process who visit the dental forum to see what is being said here. I have discussed this with one member of our adcom who finds it humorous at times about what is being said here.
So, yes, there are adcom members who have accounts here on SDN.
Yes, I've personally spoken with three of them. They all have the opinion that there are better sources of information, but the general ideas thrown out here are pretty valid.