It is a fantastic mod but why should it be in the core? The whole point of the addon system designed by Kier and Mike is to allow addon-code to run at the same privilege level as the core. Therefore I believe it should be a modular plugin, if you want it, enable it, if you don't then so be it. The core (or as I think of it the kernel) should be as lean as possible without any bloat and then you enable the plugins (modules) you want.great idea.... should made it into the core-code as an option.
I saw something like this at another website at which it was named something like:
"save this to read later"
"bookmark for reading later".
Keep the core lean!