-- Attachment is not available -- Broken by wpdiscuz

The fix above was never going to to work, because when you edit the forum post, the

attach shortcodes have been replaced by the error text, so I have to manually find the corresponding comments and forum posts and manually copy them in.

@marsm,

The option helps for new posts not the old ones. The old posts are already replaced with non-shortcode content. So please test new posts and see if the issue is fixed.