Some testing shows that “read-only” users get email notifications that include “Reply to this email to respond”. is there or could there be email footer logic that would show a more apropos and friendly text, e.g. “Topic is closed/read-only. Replies will be ignored”?
I set up a new category that has all permissions for moderators, but only See permissions for others. A “civilian” sees the Reply to respond" footer on email notifications. Ditto for a category where all can create/reply but the topic is closed, and a moderator has replied. Civilian getting email notification sees the “reply … to respond” footer.