I was actually on the phone with Star Desk researching this while Sean was on the phone w/ SEARR. Star Desk said the original agent broke the rules for sean by booking the overnight. She said no stopovers are allowed. She said that may get her in trouble, and that's why the other agent booked sean on the night flight from YEG to YVR.
So I'm not sure writing UA would be helpful as they were just following the rules after it was discovered someone else broke them for Sean's benefit.
Sean, I *did* try and the agent said it was already re-instated, and Star Desk was ready to reinstate the UA inventory. But it looks like it also involved AC from what the agent @ Star Desk said.
Becareful about writing a letter!
-nate