On my user page on the Swedish Wikipedia, for example, I have the Babel template as:

{{#babel:en|sv-0}}

Despite the zero rating for Swedish, that adds me to sv:Kategori:Användare sv ("Users of Swedish"). The same thing happens on the Portuguese Wikipedia, where:

{{#babel:en|pt-0}}

adds me to pt:Categoria:Usuários pt, and so on.

This should not happen when the rating is zero.