MoveableType uses a smart server and a dumb client. The smart server embeds comments and trackback pings into the page that they reference. This allows the flow of conversation from comment to comment and blog to blog to be more easily followed. The unintended consequence is that MoveableType weblogs attract comment and trackback spam from the attendant Google Leech.
Using tools with limited scope protects against unintended consequences, while using powerful tools like identity requires more care to protect against unintended consequences. Both comment and trackback spam can be defeated by controlling the flow of google juice. But what unknown gremlins are waiting to emerge from Typekey? Will a Typekey identity be protected against sniffing while using a public wifi hotspot?
That’s my issue with Typekey. It is much too powerful relative to the problem it addresses. Resources and value go hand in hand. I doubt that commenting has the value to command the resources to do Typekey right.
PS. Just for the record, Userland may have forseen the advent of comment spam way back when. I have no knowledge one way or the other.
PPS. Why not initially render comments and trackback pings with disabled links (i.e. something that is not followed by search engines)? And allow the links to be subsequently enabled by the website owner.