It would be good, but I don't see it mentioned that when a page is published, a current version could be written to the filesystem to reduce database lookups. That way revisions aren't read out of the database except when they are changed.
With regard to comments, they could either be retrieved from the database or written to the published file.
With this type of system the pages could actually be rendered into HTML if there were no parts that needed to be queried from the database on each page read.
