For less impact on the interface, what if the link to Anonymous Monk (not a particularly useful destination currently) was replaced by the link to a page where you can request ownership

Do you mean the link right by the title which says "by Anonymous Monk"? yeah, changing that for just this one case is a bigger impact to the UI.

requesting ownership ought to be a POST request

It's just sending a message, as a side effect of reloading the page. PerlMonks isn't particularly RESTful anyway.

tbh this was a quick-and-durty. Minimal code, minimal impact on the UI. The cost? Bigger demands on documentation, I guess.