It's not a Dreamwidth issue; it is the plugin I use for Wordpress on my main blog. The old plugin, which stopped working and wasn't maintained, did update the posts. This one doesn't. That's why there's that "Click Here to Comment" box, as well as the text that notes that "Note: Subsequent changes made to the post on the blog are not propagated by the SNAP Crossposter; please visit the original post to see the latest version. P.S.: If you see share buttons above, note that they do not work outside of the Wordpress blog."