From Donald himself.
http://forum.dominionstrategy.com/index.php?topic=876.25
It is not up to any rulebook to say that you can't use a memory aid; rather it is up to the rulebook to specifically allow it, or else you can't use one. It doesn't matter how much the game for you is not about this memorization, how much the memory thing seems tangential to whatever fun the game provides; you do not get to use anything other than your brain to handle that memorization, unless of course you are explicitly playing a variant. You also do not get to - and this is important - scrawl notes to yourself on your belly using your own blood.
Funny, you know, I wasn't really raising it as an issue, really just trying to identify who the "Invincible Overlord" was. Have I identified him correctly?
As to the playmat / scorepads in play... They didn't really bother me, although I prefer to play against people who don't use them, so I'm good with the whole ruling here. I do see where these things come from -- it's absolutely rife in Isotropic.
On another related note, I think it's a great sign for the Official online Dominion that counters are not supported.

We all knew that bots were in use at Isotropic, so when they implemented an official counter, it wasn't unexpected, and actually just added some transparency to a process that we already knew existed. I'm not sure how they stop bots from the Online Dominion (maybe, quite possibly they just can't), but at least it won't be "in the open", like it is at Isotropic, because that's really what's happened there -- the official counter has led to many people thinking this is an official way to play the game.
Cheers for the clarification all.