I think I found what’s causing these mysterious “updates”. Gallery2 embedds the session id in the short url of images if no cookie is found. Well since Bloglines and the Planet Ars Lounge (and Feedburner as I found out), don’t store cookies, the session id is there, and since the session id changes each time, the post is marked as updated. Or at least that’s my theory. Luckily gallery2 handles this for the common search engines by looking for identifying strings in the User-Agent and if it matches a known search engine the session id is not included (this is so the search engines don’t index a bunch of pages with session id’s in them). I’ve added the User-Agent values for Bloglines and Planet Ars Lounge and we’ll see what happens.

Sorry for spamming your aggregators while I was working this out, and I hope I’ve licked it.