...Wait. I had userpics in the body of an entry, and they still had http in the URL, and they were showing up anyway?!?!
*checks the "list of userpics in order added post" where all the images were broken for a while because they had http in the URL, and indeed, now they're showing up again too*
YAY!! At some point LiveJournal finally fixed the issue of userpics not showing up in the body of entries, and now I don't have to edit thousands of entries just to make entries that have userpics in the body look presentable!! THANK YOU!!
*continues looking through old entries anyway, because there are still other things in them I want to fix, especially on DW, and I figure I still might as well do that now since I already have the motivation... but at least it's slightly less hopeless now!*