For the tape, I'd added some additional text to the end of my feeds (primarily for feed readers) that read something like "The post https://boffosocko.com/permalink/ first appeared on Chris Aldrich. Reply to this post via email at blog@boffosocko.com."

I'm switching over to the JSON feed method allowed by Syndication Links plugin which should hopefully get around the issue. Otherwise perhaps I'll look into removing the additional text. It did seem nice to make it seem easier to interact with my RSS feed posts in some settings though.

Control of syndicated copies of content is definitely a difficult problem.