Is this a new class? If so, it should be named `.logo__tagline`, as tagline is a BEM element in the logo container. It would actually exist inside of the `.logo` rule, as:
```scss
  &__tagline {
    // ...
  }
```

Not only this, but if `logo` is a block, it should have it's own block file (partial). I realize Method was the first theme and it didn't follow all of these paradigms, but always leave a campsite better than you found it?