Based on recent discussions on slack, I noticed that the trait isimmutable is an exception to the rule compared to other is* traits in the language. For a concept foo we usually have isfoo as the trait, and !isfoo as the negation. However, with the concept mutable, we currently have is(not)mutable (a.k.a. isimmutable) implemented as the trait.

Would it be possible to deprecate isimmutable in favor of the more readable ismutable trait?