That seems like it might be a "good practice"? Renaming self with a constant, sigil-less variable will prevent you from losing your self?

Well, on the other hand, it looks like $dog is readonly:

lass Dog {
    has Str $.name;

    method bark(Dog:D $dog: Int:D $x) {
        say $dog.^name;
        say $dog.name;
        $dog = 'hello';
        say "bark" for 1..$x;       
    }
}

Dog.new.bark(3);

--output:--
Dog
(Str)
Cannot assign to an immutable value
  in method bark at b.raku line 19
  in block <unit> at b.raku line 24
[download]

So is using a sigil-less variable to capture self more of a style thing? For instance, to make you notice that the variable is different from other variables?