OK, from reading other posts and through a little experimentation, I think I have this figured out.
First of all, the "Modify a page" permission under "Permissions for All Pages" has the implicit "Owner" role added by default. (See attached image) This should be sufficient. If a user is the owner of a page, then that user should have permissions to edit his own page. Unfortunately, this is not how it currently works. The user will not be able to see the "Pages" menu to get to his own page to edit it.
It was suggested in another post
that a custom role be created that has been granted the "Modify a Page" permission under "Permissions For All Pages", and then add the user to that role.
Creating a custom role and going to "Permissions for all Pages" and giving that custom roles permissions to "Modify a page" does work in the latest internal build (4.1.1367 soon to be implemented in SP1). I have verified this. IMO, this is still a bug, albeit a workable bug. If you grant a role permissions to "Modify a Page" under "Permissions for All Pages", this implies that anyone with this role can modify "All" pages. This is not however how it functions, and it is very counterintuitive to have to do this. Being the owner of a page should, in and of itself, be sufficient to allow a user to edit their own page.
Previously, in the 4.1 release, the user had permissions to modify the title and properties of the pages owned by other users and although they could not delete another user's current page version, they they could delete another users previous revisions. They could also post notes to pages another users revision history. This appears to be fixed in the 4.1.1367 build. The Revision History is no longer present on the action menu for users without permissions to modify the page.
This is definitely a step forward, and it is usable, but it is still a little quirky. The custom role should not be needed for simple editing permissions on a user's own page. If a user clicks on the Actions Menu of another users page, they still see the Delete, Edit Title & Properties, Edit Permissions, Change Owner, and Move Up and Down menus although none of them function.
IMO, a more elegant, and probably simpler, solution would be to simply not even allow one user to see another user's page in the Pages list if they have no permissions to that page at all. This would keep the clutter to a minimum especially when there will be many users who are restricted to editing ONLY their own pages. In our case, as a University, we will have nearly 1000 users (faculty) with permissions to only edit their own pages and if we roll this out to students as we eventually plan to do, we could have 10,000 users who should not be able to edit other user's pages.