‘nother update: I disabled the WordPress Connect plugin. Same problem. The first comment keeps getting cross commented back to WordPress, while the second comment seems to be ignored.
Then I disabled the Disqus Comment System plugin (since my problem is comment related). Same problem. The first comment keeps getting cross commented back to WordPress, while the second comment seems to be ignored.
Rather than keep going one-by-one, I disabled AAAAAALL of them, except of course the WPBook plugin & Core Control plugin, so that I may force wpbook_cron_job to run.
Ah haaaa… This time, it cross commented both comments back to my WordPress blog, the first comment as if for the first time, and the second comment for the first time. Now we are getting somewhere.
I forced the wpbook_cron_job to run again. Checked comments again. No new comments. Seems it has now remembered that it has already imported the comments from Facebook.
Soooooo, I guess it must be one of the various plugins I had activated. Or maybe a combination of one or more? Looks like I need to do more testing. :-\