I have a ‘recent posts’ and ‘recent comments’ section in the sidebar. This seemed to create problems with the processing of webmentions, specifically with Aaron Parecki’s Xray library for grabbing structured info from any URL. It would find an apparently improperly micro-formatted link in the sidebar and take that as the URL of the posting referred to. This would create faulty likes on other people’s sites, which then would send webmentions to the wrong postings.
As recent posts and recent comments are only a navigational aid when you’re looking at things like the front page, search results and archive pages, I looked into if I can show them on those pages only. Because if those sections aren’t present on the pages of individual postings, they cannot cause problems when parsed for structure. This being a WordPress site, of course there’s a plugin for it, Widget Context. I installed it, removed the offending widgets from individual pages, and it looks like the problem has been solved.