Short description
The default attachment link [[attachment:file_name]] , is a link to an html page with the embedded attachment. This behavior is uncomfortable for the most users, because often they only want to see the attachment. And even worse, with some attachments you get a warning message, that the file can not be embedded in the browser.
To get the more common download link, you have to write [[attachment:file_name||&do=get]] which is difficult to remember if you don't work a lot with attachments in the wiki.
Better would be a configuration option for the default handling, for example default_attachment_link and a change in the file MoinMoin/formatter/text_html.py line 622:
With this, it is possible to configure
default_attachment_link = 'get'
and after that all attachment links without any option [[attachment:file]] are common download links.
Comments
As there are not any more attachments in moin-2 and you have to use transclusion syntax for showing an item on an other one this likly won't become changed. http://test.moinmo.in/images See there the Transclusions navigation element. There are different rendering methods planned.