First of all, I'm wondering why you posted this question two times.. Not necessary at all I think.
Your question. If I understand you right, you want to know when someone should use +W. In case you use Unreal, this usermode +W means that you, as an IRCoper, can see who whoises you. So you will only get "authorization" to use +W if you're an IRCoper.
You can give regular users this usermode by using "/os umode nick +W". Although I believe that you'll have to be a Services Admin to achieve that.