I can’t believe my bad luck. Flying longhaul in PE booked as LH codeshare operated by 4Y. At checkin I asked about upgrade availability and they confirmed it was available. The good news stopped there, because they said eVoucher upgrades were not available for code share bookings. The duty supervisor made several calls and confirmed this. I was certain that the rule was that upgrades at checkin were always possible and the codeshare rule no longer applies. I called the SEN line but they confirmed what the airline told me.

Did I just imagine this day of departure relaxation of codeshare restrictions, or is 4Y just being extra restrictive? If it is the former it reinforces my rule to never book codeshares, if it is the latter I know not to expect any better treatment because 4Y is part of the LH group (which I had hoped for at time of booking), and thus avoid them like the plague.