Comments content is not evaluated against the current document

Hi all,

I'd like to use a link to an attachment in a blog comment, like
[[attach:demo.jpg]]. It causes a link to
http://<wiki>.<hostname>/xwiki/bin/download/Main/WebHome/demo.jpg -
that's wrong, it should be
http://<wiki>.<hostname>/xwiki/bin/download/Blog/<blog page>/demo.jpg

I am using xwiki 2.7.

Thanks
mb