For the comments we have lots of links, such as [se] and [ubuntu.se].

I thought it would be helpful to have a [launchpad] link, so we can easily direct users to it - i.e. the bug report site - https://launchpad.net/

So from the comments:

Detect the string ppa: and make it into a link, like http://. So ppa:peterlevi/ppa would turn into ppa:peterlevi/ppa. (Wilf's comment)

[forums] point to ubuntuforums

[discourse] point to discourse.Ubuntu.com (Seth♦'s comments)

[download] go to ubuntu.com/download/desktop

[paste] to paste.ubuntu.com

[install] to ubuntu.com/download/desktop/install-ubuntu-desktop