Board Thread:General Discussion/@comment-1416490-20131211031151/@comment-16101931-20131213100458

You mean you want to have a different signature for message walls, separate from your normal one? If that's the case, there's no way to do that using CSS because there is nothing to modify.. Signatures, whether on message walls, or otherwise, are just transcluded from the text in your preferences, which may be transcluded from a /sig page or similar. But there is nothing specific in the HTML that you could select to modify, it's the same everywhere.

However, you could create another sig subpage of your username (like User:you/sigMsgWall) or something, and just transclude it on your message wall posts, with ... But I doubt that's what you're looking for...

Really, besides that, I'm stumped. I don't think there's any way to change users' sigs on message walls, except by the user putting a different sig themselves.

If that's even what you were looking for. If not then sorry, you'll have to be more specific...