As you can see, the sidebar features Meta, then the ad, then the chat ad, then Meta again, then the ad again, then the chat ad again (which fails to load), then finally related questions (once):
Props to GnomeSlice for noticing this first.
If you can reproduce this issue in Notepad of all things, that means serious business. Fixed with extreme prejudice.
Just a duplicate value in the site's ad settings, btw.