I was right about doubles. I got the webmention script working, used the @puppyrey micro.blog account to reply to @rich_text, and the resulting reply appeared both in the conversation.js script (an internal-to-m.b thing), and in the webmentions. Next step; contemplate filtering those; also figuring out how to get webmentions on-the-fly instead of only at build-time (which I can do, for conversations; same pattern might work...).

screenshot of comment appearing twice on blog