The bug seems to be that the extension will override whatever you ask to do, and copy highlighted text instead, if anything on the page is highlighted. Sometimes highlights are forced by the scripts of the website, so there’s no way around it.
It took me a while to figure out what these strange plain-text dates in my Dynalist were. They were failed link clippings.
Reproduce:
Using Chrome, Go to your facebook feed, right click a post’s date (which is where the direct link to the post is), and click “Clip this link to Dynalist”. Notice that facebook’s javascript automatically highlights the link when you right click. Now check Dynalist - it is simply the date in plain text, no link. No warning that you’ve lost that post forever, thinking it’s in dynalist.