yes the theme has an attachment.php file.
I don’t think it’s related to the theme because on post with attachments i made prior to 2.7.1 still shows the comment form for the attachment page. It’s just the ones I have made recently.
It seems like comment_status field in the db is not inheriting the post comment_status even though it is showing inherit.
I’ve tried it with different themes..with disabling plugins..and still all the attachment pages are showing as “comments closed” even though the post page is showing the comment form.