Adding details about links

CONTRIBUTING.md

@@ -13,5 +13,10 @@ issues or PRs that simply don't fit our internal engineering needs.
 PRs to the style guide should include a description of the proposal, including
 examples of what "good" and "bad" code would look like under the new rule, as
 well as a rationale for the rule in question. The description of the rule and
-the examples belong in `README.md`; the rationale goes in the corresponding
-section in `rationales.md`
+the examples belong in `README.md`. If the rationale is anything other than "for
+consistency", it should go into a corresponding section in `rationales.md`.
+Style rules that are purely about consistency do not need rationales.
+
+Individual rules should include, after the description of the rule, a link to
+that rule, and, if a rationale is being added to `rationales.md`, a link to the
+detailed rationale.