That was in fact very important missing feature. This should boost number of interactions between Engravians (did I just invented a word? :D). It will be much more easily to add comments to different blogs :)
I guess, with cross-domain authentication, it would be very difficult to implement a history of visited engrave blogs, right? :)
Every time you reach Engrave blog, you need to be remotely validated, so yes - it should be easy to add the history of visited blogs ;)