UPDATE 09:01: Nope, doesn't change the post's on-blog display at all. Must be meant for catalog and/or syndication etc.
I guess I could check the FAQ or something, but that's too... I dunno, too easy.
There's a Keywords field available in the Customize the display of this page window on the TypePad posting page, and I have no idea what the field does. Is it a way to provide keywords for searching, or a secondary category method, as it were, or...?
So this post is meant to test what, if any, display changes occur with keywords entered for a post.