pubDatetag is being written as
pubdate, with a lowercase d. I had noticed that the last few times I looked at the style's output's source, so yeah, I went to fix it.
What I hadn't realized is that I did do it correctly when I wrote the style. Something's up with LiveJournal spitting it out in lowercase instead of the proper mixed case. I opened a support issue about it (which is also my first experience filing support issues). As I wrote to Mark, if for some reason the bug can't be fixed, I'll just have to write a replacement RSS 2.0 style that uses