That's something I miss in phpBB3 and I've seen such a feature in other forum software like IP.Board, vBulletin etc to mention a few.
Later on I found out that this feature can you actually do right now, of course you need to do it manually like my post. Just take a look on the quoted post and click on the posters link.
If that kind of feature was included in the phpBB code then it will save a lot time when someone is reading the post and want to back to the actual post just to read it again in a previous thread page.
I would also like to comment something about the idea that AmigoJack has and I know that IP.Board already have that kind of feature in their current forum software, but I think it could cause unnecessary issues by doing that.
Because what will happen when someone decided to leave the forum or a member was banned and the posts for that member aren't deleted. A feature like this "Quote with a link to quoted post" idea could be broken and could sometimes be hard to fix.