Today I learnt that Emacs will do a best-effort parse of expressions in comments too, unless you set parse-sexp-ignore-comments.
That's all well and good until org.el has ASCII smileys! https://github.com/bzg/org-mode/blob/4d8d7d6cb42e388572b4f5d227e9b3c9da6ca4a7/lisp/org.el#L4815-L4816 ("unbalanced paren")