In reply to mark k..

Good points. For me, personally, I'm not so bothered, as I use Epoch which does allow the comment box to be at the top (or you can simply hyperlink to the comment box, even if there are hundreds of comments). Although that still doesn't really solve the logged-in/non-logged in issue you highlight.

It never fails to amaze me that they don't tie it back to your Gravatar/Wordpress.com account, if you have multiple emails addresses connected based on what types of blog you're commenting on (or running).
There could be a simple dropdown box that allows you to choose which email you wish to use - job done.

Or am I missing something about this solution (for example, would the blog need to be running Jetpack comments)?