What makes this strange tax even more absurd: as you are your own landlord, your property interest rate becomes a business expense of your hypothetical rental company. So you can deduct your property interest from this income tax on the fictitious rent you pay yourself.
In effect, it is unattractive to fully repay your mortgage (you just leave enough debt to avoid the income tax), and Switzerland has the highest household debt in the world. By a large margin [0].
[0] https://en.wikipedia.org/wiki/List_of_countries_by_household...