Contacting users via their wall is commonly used for notifying about tours, etc. and other things. However, there are a lot of users that check "My Updates" section more than their wall (just in-case their wall is generally dead, so they don't look at it many times. Showing the mentioning of the username on a post in "My Updates" can help to contact users much easier. Like in this way:
< Username > with the link of the user's profile.
On My Updates, it will show something like this: "your name mentioned < time > by < username >"
So, is this feature a good idea? It might be a very minor suggestion, but I guess it can be helpful especially for contacting users for tours, in case the user may not always check "Recent Activity" or questions, answers or their wall.