I may be wrong but here's my 2 cents...
The avatar that is displayed for each post is a snapshot of your user profile. That's the reason why the post count always shows the newest number. The same would be true for location/avatar/status etc.
The sig however, I think, gets added to the message and is saved at the time of posting. I think instead of saving the sig in every post, the bb sw adds a flag that indicates if the post has a sig. And while displaying the post, if the sig flag exists, then the sig from the UP is displayed.
I believe there are third party mods that make sigs retroactive.
Its been a couple of years since I've played around with phpBB, so if this is incorrect, I apologize.
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Anand (This isn't a sig
![Wink :wink:](./images/smilies/icon_wink.gif)
)