Thanks! This is working great. Interestingly, in the time since I originally reported this, I came across a related need for a Post Edit report. Spammers are posting innocuous things and later editing them to contain links.
The current Post Edit report only shows when User A edits User B’s post, which is definitely what I originally requested. It’s a little confusing though that it leaves out when User A edits User A’s post.
I think my use case is adequately solved by the Data Explorer query described here, so I’m not requesting a code change, but I would recommend tweaking the title of this report to something like “Cross-user edits” or similar. 
Thanks again for all your help.