Just to clear things up, I think this is what he means:
You get a new signature, and you change it in your User CP.
Now after you update your profile with the new signature, obviously the new signature will show up in all your posts after that point.
What he has noticed is that your new signature does not show up on any of your OLD posts (OLD, meaning posts he made
before he updated his Profile with the new signature).
I'm not sure why this is, but maybe you have a better understanding of what he is asking Pan, and possibly know the reason why this occurs/how to fix it.
