Regular users cannot access the Tools>Who's Online tab
#2
It is not available to the public because vBulletin has had some scaling issues from the start and the Who's Online was one of those features that takes resources.
Aside from the Online status indicator shown under a member's post, I believe you can add them as a Contact/Friend and then use Open Contacts PopUp in the Quick Links. Provided the member has not set their profile to be invisible.
Aside from the Online status indicator shown under a member's post, I believe you can add them as a Contact/Friend and then use Open Contacts PopUp in the Quick Links. Provided the member has not set their profile to be invisible.