I am building a MU site with a teacher blog (buddypress) at the center and a bunch of student blogs hanging off of it. I make the student blogs by building a template and cloning it together with the batch create plugin. Very good stuff!
It so happens that I have two sample comments attached to the replacement for the Hello World post (in this case, it's Hola Mundo). The two comments weren't getting copied across by the plugin so I cracked open the plugin file and thanks to its VERY clean and consistent design, I was able to add support for Comments with just a few copy/paste/edit steps.
I tried to attach the "-dtk01" branch of version 1.4 here, but ZIP's and .php's aren't allowed. Drop me an email if you'd like a copy. Hopefully you can fold my changes back into your code, since they are literally just clones of the "posts" support with text substituted with the string "comments" - this was a very fun experiment for a plugin coding noob.