One example of delta/compression schemes is the rather old-fashioned
notion of attempting to edit down the material to which one replies.
Granted, it relies on assumption rather than knowledge of stored local
data, but especially for network archived material, the failure mode
isn't very discouraging.
> I have enough disk for something like a shallow traversal of the links
> off of the most recent page grabbed, but it would need a real traffic
> shaper to not get in my way.
Early versions of navipress had a background fetch mode, where
'press would attempt to follow links as long as they (a) did not
appear to be too large (heuristically driven) and (b) did not
conflict with foreground (only application local) requests. I don't
recall any user feedback on this feature, but it may be that it
wasn't carried forward past '94 or so.