2008/2/6, Stephen Bain stephen.bain@gmail.com:
The recentchanges table (used for Special:Recentchanges, watchlists etc) stores both the old and new page size, but the revision table (used for history pages and for Special:Contributions) only stores the new page size, so you can't calculate the change unless you look up the previous revision too. This would make Special:Contributions pretty expensive to run, so I doubt it's feasible.
Just thinking out loud here: Might it be possible to have a Special:Recentchanges with only edits by a certain user, or even just only bot edits, like there now already are possibilities with only logged in/anonymous edits etcetera?