Originally Posted by
LupineChemist
It's an EU ID card that they call a "passport card" so people don't go nuts about ID cards. It's functionally the same as any other EU ID card within the EU. As it's an Irish ID card, it's also valid in the UK which is particular to Ireland rather than any other EU country.
There's still a lot of issues with using EU ID cards in the UK though. I recently witnessed a conflict between a pax who has pre-settled status (thus is eligible for entry into the UK with an ID card) and a BA gate agent at LHR who has decided that ID cards are not accepted to depart from the UK. It's a major PITA. I imagine Irish passport cards holds are in a marginally better position but probably not completely prone to the confusion.
(Not to diverdge from the topic here, but I still can't wrap my head around why UK doesn't accept EU ID cards unilaterally, like some Balkan countries do - clearly they've been good enough proof of identity for decades, and since they no longer stamp EU passports anyway, I really don't understand why is a passport better than an ID card for the British authorities, especially since EU ID cards are now biometric too.)