(Bug 4176) Fix errors in notif username display

Previous commit displayed original requester's display name
in all notifs relating to a support request. It should display
username not user-set display name, and should display u/name
of person who triggered notif, instead of name of OP.
Merge pull request #565 from kaberett/bug4176-support-notifs-fix

(Bug 4176) Fix errors in notif username display