Spectrum wrote:
it used to happen to me, then I realised it was autofill that was changing it so it could be that for you.
Ahh Spectrum may have finally found the reason this has happened to a couple people. If you are editing anything on your profile it is possible autofill could change something even on another tab. Since that is all clientside there's not much we could do. The forum software infact does not have any kind of functionality or storage for reverting to old signatures so on the serverside it is technically impossible.