As a partial alternative to the "comment admin page" which is "missing the ability to edit Author and Url fields": how about using something like the "Seven" theme as your "Administration theme"? By using that theme, and navigating to
admin/content/comment, you can use the "edit" link to the right, so that you'll be able to edit fields like "Author" from there.
For the sake of completenes, be aware that there is a Bootstrap issue about styling comments which I believe is somehow related to this question (current status = postphoned). And it has this related issue: Add a comment.tpl.php to base theme, in which it says "There is no comment.tpl.php in the base themes, so it is pulled from core."
According to the first issue, it seems that it might be a good idea to use some of the typical alternatives for styling comments using bootstrap, or any of its sub-themes. I.e. something like Panels or Display Suite.