If you write a comment and drag and attachment to the comment
box then it will show inline with the comment.
Image thumbnails should still show in the sidebar too though.
Perhaps it wasn't able to detect the mimetype for some reason (it
doesn't check the extension so being .jpg doesn't make it an image
- it has to load the image and check the mimetype).
Was this a once-off, or is it happening for all images? If it's
happening for all images, it might be because the function
"finfo_open" is missing: http://php.net/manual/en/function.finfo-file.php
(Bugify cannot check the mimetype without that function).