I've reviewed all the settings; but it appears as though the Signature Permissions of a Secondary Usergroup isn't overriding the Primary Usergroup settings.
Things to note:
Primary Group DOES have "Allow Users to have Member Groups" set to "Yes"
The test case I used was:
Primary Group set to Registered:
Signature Permissions "Allow Font BB Code" = NO
Secondary Group set to Test:
Signature Permissions "Alloew Font BB Code" = YES
In the "Edit Signature" page, the setting at the bottom of the page reads:
Allow Font BB Code No
Things to note:
Primary Group DOES have "Allow Users to have Member Groups" set to "Yes"
The test case I used was:
Primary Group set to Registered:
Signature Permissions "Allow Font BB Code" = NO
Secondary Group set to Test:
Signature Permissions "Alloew Font BB Code" = YES
In the "Edit Signature" page, the setting at the bottom of the page reads:
Allow Font BB Code No
Comment