The only advantage from alphabetizing rules is perhaps slightly faster scanning of rules, but I don't think it is even very helpful in doing that. You generally don't have that many rules in a single style anyway so it's not a problem that needs solving.

However, by grouping related styles I think there are a some small yet worthwhile advantages. Grouped styles can reveal intention, while alphabetizing does not at all. Grouped styles can also make refactoring quicker and less tedious.