Since version 2.7, WordPress use wp_list_comments() to display comments instead of the old loop. If you only want to show comments without trackbacks, that’s easy to do, just add a parameter: We also need to consider other things, like re-count the comments, list trackbacks and many bloggers prefer to show trackback links only, without excerpts. [...]
Separate Trackbacks from Comments in WordPress 2.9
Since version 2.7, WordPress use wp_list_comments() to display comments instead of the old loop. If you only want to show comments without trackbacks, that’s easy to do, just add a parameter: We also need to consider other things, like re-count the comments, list trackbacks and many bloggers prefer to show trackback links only, without excerpts. [...]