0. have a bugzilla with allow_attachment_display off 1. have an account (and be logged into it) on a bugzilla, e.g. mercurial's 2. load an attachment, e.g. https://bz.mercurial-scm.org/attachment.cgi?id=1901&action=edit 3. click the preview button actual results: see blank pane, and get confused. expected results: instead of showing me a blank thing that makes me think i'm seeing nothing previewed of the attachment, show me "(no comment text to preview)" or something similar (probably italicized)
Step 0 is useless. This is independent of the preview box.