IT WAS ME
READ ON FOR THE SECRAT
I can't do it the old way anymore, just like everyone else. Editing the thread's original post doesn't work anymore for some reason, so I'm only able to change thread titles if I double-click the name of the thread and then quickly hit Esc to stop the page from loading. Double-clicking brings the thread title up in a text box, which can then be edited.
This may only work for mods. Non-mods should try it on their own threads and see if it works but DO NOT CREATE THREADS TO TRY IT OUT, FUCKERS. I AM A SERIOUS.