Okay! LJ tells me that there had been a bug in the admin console, but they fixed it in late June/early July. Unfortunately, it doesn't retroactively fix existing friends, so they said I would have to defriend and refriend everyone who I had added via the admin console before the bug was fixed. It must've been a bug that was introduced into the console at some point since people who were friended quite some time ago weren't affected (but the recently alumni were when they were defriended and refriended to the alumni filter).
Anyway, I purged my friends list and refriended almost everyone, so if anyone who couldn't see
this locked post could try to view it again and let me know if you can now, I would appreciate it. I hit the 200 friend adding limit somewhere in the middle of townies, but all students, alumni, and teachers were re-added.
It's not a big deal if you don't lock posts as a rule, but if this works and if you're like me and want everything in working order (and might be locking naughtier posts), it's a good idea to purge your list and rerun the friending list. :)
ETA: Seems to have done the trick so far, yay!