I'd like the ability to "tag" members in threads.

For example:

If we are in a long thread about optics and I see a member who is obviously a SME, I'd like the ability to tag that user with something like "optics SME". This tag field would reside underneath the user's avatar/info on the left his/her posts. The tag I assign the user would only be viewable by me.

This feature would allow users to better tune the noise/useful information ratio to their own liking without influencing the group involved in the thread.

As far as tags being persistent... I dunno. Maybe they are just active for the one thread you are tracking or maybe they stay attached to the user's profile you assigned them to.

Little Pony would be in everything.