The way that attachments are ordered in JIRA is very confusing.
In spite of what JIRA-8842 says, they are not ordered by date.
As far as I can tell they are ordered by descending order of date within ascending order of filename.
I can't see the point of including the file name in the order, unless there is a strict naming convention for attachments.
Furthermore, the only way to tie the attachment comments to the attachment is via the date.
The attachment comment does not appear in the attachment screen, and the attachment name (or link) does not automatically get added to the comment, as for example is done in Bugzilla.
This all makes it hard work to use attachments.