Comments never show display name

[Saenic]

This bug is easy to reproduce:

1. Write a comment while logged in
2. Change your display in the Admin panel
3. Write another comment

Your first comment will show your old display name while your 2nd comment will show your new display have.

Technical details:

For not logged in users Wordpress saves the user name directly in $comment->comment_author. But for logged in users Wordpress is supposed to leave the $comment->comment_author field blank and instead fill out $comment->user_id. But it doesn't. When I do a var_dump on the $comment object, there is no user_id field and the comment_author field has my currently set display name in it.

The get_comment_author($comment_id) function checks if $comment->comment_author is empty and then looks for the $comment->user_id.

[SergeyBiryukov]

Duplicate of #10653.