[complete] Add a comment about flex style priority

Author: alexander-yakushev

cider-completion.el

@@ -297,6 +297,8 @@ Only affects the `cider' completion category.`"
     (unless found-styles
       (setq found-styles '(styles basic)))
     (unless (member 'flex found-styles)
+      ;; This expression makes sure that 'flex style has a priority over other
+      ;; styles, see https://github.com/clojure-emacs/cider/pull/3696.
       (setq found-styles (apply #'list 'styles 'flex (cdr found-styles))))
     (add-to-list 'completion-category-overrides (apply #'list 'cider found-styles (when found-cycle
                                                                                     (list found-cycle))))))