From a worldwide perspective, it is incredibly uncommon, and just from the basics of this issue it is clearly uncommon in Switzerland as well. The standard keyboard layout in Switzerland is QWERTZ (across all of its language speakers). This website is generally only used by the Swiss.
I mean, if a basic authentication mechanism of a critical government website doesn't work with a keyboard layout, odds are incredibly likely that said keyboard layout is uncommon. Like not one of the developers, testers, stakeholders, or even other users had a problem -- and this isn't a problem you can just ignore -- so it probably isn't that big of a deal.
I'd understand a developer in e.g. America not being aware of it, but to one in Switzerland, France is right next door. A developer working on something as important as their government login system should be well aware of different keyboard layouts surrounding, and leaking into, their country.
Yes, I understand where France is relative to Switzerland. But the basic fact remains that not one of the developers or testers or stakeholders encountered this, and it was so rare apparently the very first person to encounter it -- given that it was literally a blocking issue, and not just some transient issue -- is the linked article.
Is it a regrettable bug that made a poor assumption that breaks in special cases? Sure. Is it "Dunning-Kruger" (groan), or some demonstration of how stupid the developers are? Give me a break.
The Dunning-Kruger thing wasn’t meant to disparage the developer and certainly not to call them stupid. It’s simply a reflection on not knowing what you don’t know and thinking you know more than you do. Everyone goes through that.
I mean, if a basic authentication mechanism of a critical government website doesn't work with a keyboard layout, odds are incredibly likely that said keyboard layout is uncommon. Like not one of the developers, testers, stakeholders, or even other users had a problem -- and this isn't a problem you can just ignore -- so it probably isn't that big of a deal.