It may be possible to turn all signatures off
Just checked, and here's how to do it: hit "User Control Panel" in the log in panel under the tf2maps banner at the top of the page, then hit "Edit Options" in the toolbar on the left side, and scroll down until you find "Thread Display Options".
There, you can turn off Signatures, as well as Avatars and even images in general if you're running on mobile. Also, if you are a VIP or Veteran, there is even the option to collapse signatures that works much like a spoiler tag, allowing you to open them up if you really desperately want to remind yourself how much effort Berry put into making those stamps.