Maybe I am misunderstanding your ideas but I guess I don't see the benefit of visiting Tumblr's RSS reader to read Tumblr. Why not just read from Tumblr's website at that point?
I think the original commenter's point was that they frequently use Tumblr's current method of reading other Tumbls, and they would prefer that other web content appear there, too.
It's not visiting Tumblr's Reader to read Tumblr - it's visiting Tumblr's Reader to read everythign.
