I prefer a dressing room with a mirror, but like others, if I like the garment, I want to see what it looks like from all angles, so I go outside the stall to do so.
I do have one seminal experience of communal dressing rooms, but it is a far, far cry from Aritizia's.
Decades ago, when I first came to DC, I was introduced to the late lamented Loehmann's. It was a great place to get designer wear at a discount, but you did have to brave the group dressing room. There I experienced both the horror—public nudity!—and hilarity of the freewheeling commentary—everybody's grandma, mother and little sister were there and they all had opinions! There were a couple of Loehmann's near me—one in Rockville, MD, and one further out in No. Va. The one in Va. was a bit more staid, but Rockville was a rollicking store. Yes, the Loehmann's group dressing room was certainly a judge-y place, but never in a mean way. It was also funny and kind and there was always someone there to extricate you from a stuck dress, wayward lingerie or too tight pants. Or to tell you, "if your husband doesn't tell you you look gorgeous in that dress, call me. I can find you one who will! I miss the Loehmann's experience.