tokens authors can use in the class attribute, but authors are encouraged to use values that describe the nature of the content, rather than values that describe the desired presentation of the content.
specification section on classes repeating the assumed “best practice” that… …authors are encouraged to use [class attribute] values that describe the nature of the content, rather than values that describe the desired presentation of the content. …there is no inherent reason to do this. In fact, it’s often a hindrance when working on large websites or applications.