On the topic of back rooms…
Even if you get an offer in one of them in private, when you come out with your SA and bag box to go to the register, other people in the store can stop and point at the box and say to your SA “is that a Birkin? I would take one of those”. Yes this has happened to me, multiple times even, and I’m willing to bet that I’m far from the only one. (Aside, both times it happened with me it was actually a Kelly so technically no, it wasn’t a Birkin

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This of course pales in comparison to someone who was offered a B30, begrudgingly took it (she wanted 25 like everyone nowadays even though she told her SA “I’d take any size”), then while paying saw another client go into the back room with a smaller box (a B25), angrily opening the back room door and saying “I want that one instead! Why don’t you give that to me?”. I didn’t directly witness this incident but it happened at my store.
I did, sadly, witness / overhear incidents of someone shouting / berating / calling SA names in the middle of the store for not getting a bag. And the bonus variant where they were doing it in a foreign language, in which case it went on for way too long before the SM caught on and reacted. And an extension of this, once I was in store chatting with my SA and a new SA who was hired recently, the new SA mentioned she experienced crying because of a client for the first time. My SA half jokingly half sadly consoled her with “congrats on unlocking an achievement, it’s ok, you will get used it”.