I'm under the impression of that definition that an "author" can write and edit pretty much anyone's posts. What I would like to do is set it up so they can only write and edit their own. No messing with comments or anything. I'll give the role manager a shot to see what I can do, but with as many people signing up as there will be, I would still like it to be automatic.
I'm sure that there may be a way. There has to be a file somewhere that defines the automatically selected one to be the "Subscriber" and it could be changed in that file. I'll play around with the plugin to see what I can find.