Markdown Github style attachment does render correct in preview but not on page

When adding a comment and referencing an attachment with Markdown support enabled, it looks all fine
doing it like this:
[attachment description](attachment/16800/test.txt)

and the preview looks right, however when I save the output looks
wrong and is not an active link.

This gets rendered:
[attachment|attachment/16800/test.txt]

So I have to use this format after all as referenced here:
https://confluence.atlassian.com/display/CONF28/Linking+to+Attachments this works:
[PDF document about linking to attachments|^Linking to attachments attachments.pdf]