- Create a topic and make the lead post a wiki post.
- Optionally add some replies.
- Lock the topic.
- It is no longer possible to edit the wiki post.
- It IS possible to edit the wiki post.
While it’s still possible to remove the wiki option from the post in the locked topic, if I assumed that locking the topic would prevent edits to the wiki post, I figure maybe I’m not the only one. (But history has shown that’s often wrong!)