Tumblr posts don't care about the last URL portion, it's there only for presentation.

blog.com/post/[id]/[title]

where [title] is completely ignored and can be anything. For example: http://kurtvarner.com/post/19347794553/random-title-no-relev... will link to the post. The original title his post had was "A Man, a Car and His Startup" which became "a-man-a-car-and-his-startup" but the URL was changed to "man-car-startup" so now when submitted it's a "different" URL but Tumblr treats them as the same.

Ah thanks, that was the mystery I was wondering about.

For the record, the poster of this is not Kurt. I am Kurt. I have no idea who the poster is and why it was double posted from yesterday.