FNM/AVR Prerelease - Phil's Rambling Rants
That was bizarre. The closing quote in my cut tag was a Unicode closing quote instead of a generic ASCII quote mark, despite being typed in an editor that shouldn't have tried to do such a thing, and which I don't believe was displaying it as anything but a generic quote mark. I didn't see the problem until I used the LJ edit entry interface instead of my client.
As to why I can't seem to remember to refresh my own journal page after I post to make sure the post doesn't have any formatting stupidity, I couldn't say.