Uhm... This may not be a bug so much as it is my own stupidity.
I, for whatever reason, went into the "tools" section and clicked on "account recovery". I remember having an account on the old forum, yet didn't remember if I had linked my new account. So I went ahead and put in my password to recover the old data. "Maybe I have old posts that I'm not getting credit for, or maybe I'll have my real sign-up date on my profile!", thought I. "Truly these are exciting times!"
Upon doing so, I found my reputation reset. Previously, it was... 325-ish points total? It is now 0.
.... Halp?