Lupin saw Harry & friends on the Map while they were under the Cloak in Book 3.
Yes...long before Rowling decided to make Harry's cloak legendary.
I don't have any solid proof of it, but too many things don't match up if you assume that the Potter Cloak was a Deathly Hallow from the beginning, starting with the fact that no one realized that the idea of a functioning heirloom Invisibility Cloak is apparently an oxymoron, and definitely including that Moody's eye (buffed to an insane degree in MoR) and a toy invented by four pranksters in their teens (also buffed in MoR, if to a lesser degree) are able to see where Death may not.
Update: Discussion has moved on to a new thread.
The load more comments links are getting annoying (at least if you're not logged in), so it's time for a new Harry Potter and the Methods of Rationality discussion thread. We're also approaching the traditional 500-comment mark, but I think that hidden comments provide more appropriate joints to carve these threads at. So as of chapter 67, this is the place to share your thoughts about Eliezer Yudkowsky's Harry Potter fanfic.
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: one, two, three, four, five, six. The fanfiction.net author page is the central author-controlled HPMOR clearinghouse with links to the RSS feed, pdf version, TV Tropes pages, fan art, and more, and AdeleneDawner has kept an archive of Author's Notes.
As a reminder, it's often useful to start your comment by indicating which chapter you are commenting on.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: