I've recently deployed this trick on my company's confluence instance (with an HTML macro) to create a "poor man's" link shortener that allows me to change the link target after the fact.

Also recently deployed it as a very simple server side denounce: when the client first accesses page X a long running operation is dispatched. Subsequent requests for the same resource before it's done processing return a plain HTML response that says "Still thinking about it" and meta refresh after 1 second.