I'm not sure if I'm following you, can you please provide us with example, as there is one scenario where posts with attachments are shown to author and admins etc. so I'm not sure if we are talking about the same thing ?

I mean at the forums, when one makes a post, they can leave the text empty and just attach something to it (their reply say to some excercise/project as a .PDF/.DOC etc.). But in that case the "mark as answer" doesn't appear for that post (I guess cause the text body is empty for that post), whereas it should (the attachment is the answer)

In case you add an attachment and try to post empty post you should get the "Please enter a value for 'Please enter your post'." validation message, in case you just leave the post empty with uploaded attachment this post is unapproved so in order to get the mark as answer you should first approve the post and then get the mark as answer.

Let me know if that was the case ?

Regards

why is it unapproved? because it can't pass through the spam filter? but in that case any post with attachments would have to be unapproved