Erik,

there's no much reason in storing/restoring EA in an ISR, as EA's state is known: it must have been set if the interrupt occured...(unless one calls the ISR directly, which is an another very bad idea).

Not to say that there's no much reason to disable interrupts in ISR - same and lower priority interrupts are disabled anyway regardless of the EA state (due to internal priority mechanism, which cannot be explicitly manipulated); and only in very extreme cases is there a real reason to temporarily disable higher priority interrupts in an ISR.

JW