(I could swear there was a previous topic on this, but couldn’t find it.)
The post above pretty much sums up our stance on “canned replies”. There are apps for this functionality on virtually all desktop platforms, so bundling it in Discourse core seems a bit overkill.
If you want to make/commission a plugin, I imagine @cpradio’s Pull UI plugin would make a great reference, since it adds a button to the composer toolbar, has a UI and inserts text into the composer. The only other thing you might wanna do is limit this button to a particular group.
Man, I kinda wanna see someone take a shot at this plugin now 