Thank you for reading,
I added custom fields to the comment form, and saved the input in the DB, following this tutorial http://wp.smashingmagazine.com/2012/05/08/adding-custom-fields-in-wordpress-comment-form/comment-page-1/#comment-115187
Now i'd like the meta-fields in the comment form to auto-fill after the user has commented once.
Just like wordpress does with the Name, E-mail and Url; once you've commented the value stays in the fields. However, wordpress does this with $commenter['comment_author'] and this array doesn't have the data I'm looking for.