Argh. I did not obsessively check every single day in the calendar, but it looks like I now have a buttload of duplicate posts prior to, um, looks like 29th April 2010 (see end of April 2010 page). Similarly I have a lot of duplicate posts up to around the same time in my other journal arethinn, but I am not sure if any of those are new or if they are just undeleted leftovers from a long-ago import job which splatted in the same way (I have a post from June 2010 complaining about it). I thought the importer was supposed to know not to do this?

I don't know if it's possible this could have anything to do with it, but I can see from the posts at the end of April 2010 that I renamed myself over on LJ at that time (that account has had... I think three names counting this one), and arethinn has not only been renamed twice itself, but here on DW mark kindly did some manual journal name-changing or -swapping for me (in person at a meetup in the east bay? so... 2010 I guess?) before rename tokens were an implemented feature, so I don't know if that might be mucking things up somehow...?