Duplicate Canonical Tags on Single

What steps will reproduce the problem?
1. Just be on a single page/post.

What is the expected output? What do you see instead?
Expected, only one canonical tag. Insted, two display, they don't display on 
top of each other one is high in the head order, the other appears just above 
the scripts.

What version of the product are you using? On what operating system?
9.7.8 clean install, no plugins, etc.

Please provide any additional information below.

If you completely comment out the call for the canonical function in the 
header.php and comment out the function in header-extension.php in Thematic, 
you will still get one, this one will swap out correctly with SEO Plugins. It 
is almost as if nothing is required of Thematic for the canonical tag.

If i go into includes wp-includes/default-filters.php and comment the 
rel_canonical out there, it does remove both instances (with Thematic's 
commented out also). It looks like wordpress is providing this functionality 
and it is no longer needing support in Thematic. Was there a time when WP did 
not have it and Thematic added it and now it is unneeded?

Original issue reported on code.google.com by snix...@gmail.com on 29 Jul 2011 at 10:17

marcodeltongo / thematic

Duplicate Canonical Tags on Single #118