The forum FAQ says I can edit my signature by editing my profile. But if I go to edit my profile and Customize Profile, all it gives me is a bunch of color choices, and there is no field for signature text.
Answer: Customize Profile is not the correct location. Instead, Click on Forum Actions > Edit Profile. Then on the left you will see a list of options. One of the options is Edit Signature.
For me it looks like it is under profile->edit profile button->account tab scroll to "Conversation Detail Options" group and there is a LINK "Edit Post Signature" that opens a popover.
Very inconsistent UI. I could go on a long rant about not using hyperlinks for things that are not documents. But idiots have been doing that since IE 4 assimilated the Windows 98 desktop interface.