That's actually a very cool metaphor. And yes, I agree. Kudos aren't as awesome as an actual comment, but they're still nice to get. Now, if they were all I EVER got, or if I got more than the few I have, they might start to annoy me just because the email notification is always the same, and never really says anything -- but until that time, I'm okay with them. :D (and I wouldn't be surprised if the AO3 team tweaked things so people could opt out of notification or something.)