Dynamically create a page?

First it’s important to understand pages don’t get created “at the root” or anywhere else. They are assembled from template(s) and database content when someone clicks a link to view them.
Assuming you don’t want to allow anonymous posting (which would be a spam disaster), you could set it up so people can sign up as contributors, and after the owner approves them, they’d be able to post. It might be easier though to look for a guest book type plug in and use that instead.

I would:

A) Use this plugin properly configured to allow users to register, but to provide more information that the WP default.

WP-Members. Once a user is approved they can post etc, but that post will need approval per settings…

B) Each obit will not be a Page, but will be a Post.

C) The default blog page will show these in reverse chronological order.

D) Monthly and yearly archive pages can be found easily by just adding the default Calendar Widget (which will shows days with posts too) and the Archives Widget (I like it as a drop down, but it can be used to display all months sequentially that have posts)

E) The default search will help folks find posts (assume post title is the persons full name)

You can see this in action here.

So quite doable..

As for comments, I wrote this up and I also use the Askimet plugin at that site (to help reduce comment spam).