I've just moved an SMF board from one server to another and gone from 2.0.13 to 2.0.15 via doing a clean install of 2.0.15 on the new server.
One of the mods is asking me what happened to the ability of a mod to see what posts, profiles etc an IP addresses is looking at via looking at their profile, down to being able to see who they were PMing. ("It would say something like 'sending PM' and then the user account number.")
My guess is that this was done via a mod, but a) I can't see any obvious candidates in the mod files that the old server had, and b) can't find anything like this in the list available for 2.0.15.