Having read the Terms of site, openSUSE Forums terms and conditions I couldn't find any obstacles for a user to write a religious quote in his signature. By quoting in a signature the user is not, in my opinion, violating the forums T&C in paragraph
Board Content:
"In recognition of the diversity of backgrounds of the Members and in the interests of community harmony, religious or political comment is not allowed. Messages personally attacking, calling names, or otherwise harassing or being condescending to another forum Member or any ethnic or religious group will be deleted."
or Signatures:
"Signatures may contain up to 256 characters (including spaces) at the forums' default font size and one image. All images must be under 100 pixels wide by 40 pixels high. Links to external sites shall not contravene the clause on Advertising/Spam. Members in violation of this rule will be given an opportunity to adjust their signature within guidelines. If the appropriate action is not taken within 2 days, the signature will be removed by staff. Only trusted users are allowed to create/use signatures. Trusted user status is obtained automatically based on time in membership and number of posts."
As the user is not making a comment or attacking a group.