I believe most people didn't realize this big problem. Some do, and they struggled to fix it. The current trackback handler twp-trackback.php "accidentally" send 302 redirect to the post/page if the trackback call is not a real trackback. This cause my blog SEO Web Designer Binh Nguyen to have some problem with Google.
I had 2 viable solutions:
Solution 1: I made a plugin to handle the fix for that. But that will enforce 301 by default on all redirect that didn't clarify the direct code.
Solution 2: I modified the wp-trackback.php file and inserted at line 65 a second argument value 301. Which change the original:
I wonder if the wordpress team could please implement this code from solution 2 so that people don't suffer from loss of PR.