Jeremy, it appears that when enclosed within the CDATA wrapper the HTML tags are interpreted as characters whereas, when not within the wrapper, they are recognised as tags and ignored when appropriate.
Micro.blog handles mine fine, even with the CDATA but I think the issue you are having is with Known itself. When I look at the RSS feed for your status updates (https://stream.jeremycherfas.net/content/statusupdates/?_t=rss) it contains the truncated text so micro.blog is working with what it is given. As the posts have no titles I would expect the title element to be empty.
Why the character lengths of each title should be different though I don’t understand. It’s obviously doing some sanity check to make sure it doesn’t cut off in the middle of a word but even then doesn’t appear consistent.

:)