On TNFF, I don't think tagging worked, but here it does, if you've enabled it (Profile>Edit Profile>Notifications and tick the appropriate box, your choices are automatically saved).

Basically, if you type @username (where the username is found by hovering over a member's profile picture or member name) in a post (your username is NOT the same as your Display Name: you can all change your Display Names if you want to - Profile>Edit Profile>Personal, then type a new Display Name and click Save Personal Settings at the bottom - NB Nifty ), that user/member will get a notification that they have been tagged in a post.

More info in detail here: support.proboards.com/thread/483612/tag-members

Edit: This post has been updated by this one: theotherfrenchforum.freeforums.net/thread/1323/tagging-members-ffs-nifty