Travelling on UA with another 1K.
Used my certs to upgrade the return, called the flashy new Polish Centre to have
the outbound upgraded with the certs of my companion.
Friendly, friendly agents tells me that he needs to ask supervisor to do so .. me
thinks this is because I asked him to use another person's SWUs..

But no - today my balance shows that I have been pulled 3 SWUs - 2 for the
return, 1 for the outbound. And my companion has been charged 1.
Now that would not be a big surprise if the trip wasn't on a single PNR!

According to the HNL and DEN centres and according to a written confirmation
from Elite Voice upgrades for one sector of a multi pax PNR can only originate
from one single source. A supervisor from HNL who tried to do this for me
even told me that the system would simply not allow applying upgrades from
several sources...
So now I wonder what software tool the PCC has, HNL doesn't ?

That is wrong. My wife and I often upgrade a single PNR from two sources. All you need is an agent who knows what he/she is doing.

Odd. I was under the impression that they were correct.

Upon check-in, yes it works. But never so far had I got this working ahead
of time. Not with SWUs, nor CR1s, nor 500 milers, nor miles, nor paper certs.
So where do you call to get it right?
My experience is with stevenshev so far.

Once I had upgraded online, where it took all the upgrades out of my account. So I called 1P reservations, and the agent fixed it so that my mileage upgrades were taken from my account, and hers were taken from her account. Another time, I did it all in person at ORD ticketing.

I am impressed mahasamatman. It is interesting how one experience can
be so different from another!

I do this also. I have had an agent tell me she couldn't do it without talking to a supervisor. But other times the first agent I call knows how to do it without any question.