I've noticed that this question on Math SE is listed under favorites in my network profile, but not for Math SE account. I don't recall ever favoriting it, except when I tried favoriting it and unfavoriting it to get rid of it (this did nothing), so I believe it should not be listed as a favorite under any of my accounts (the question also says 0 users have marked it as a favorite).
Is this a bug? If not, what is going on?
Note: I previously asked about this on Math SE Meta (now deleted) since I originally thought is appeared as a favorite on my Math SE account, but I didn't get any answers.