Most users of Gentoo hardly take a look at the (installation) documentation when their installation has finished. After all, being a rolling distribution, there is little need to take a look at the instructions again. And for most Gentoo users, changes that are needed to be reviewed by existing users are pushed to them through news items (see eselect news) or ebuild warnings.
For SELinux users, since we're still improving actively (but also often lagging behind in updating our policies to reflect recent changes) I've decided to keep track of changes in the SELinux Handbook as a separate chapter. With this information at hand, existing users should be able to see if there are any changes needed on their part to stay up to date.
I haven't used news items here yet, since we're still too volatile, but I do plan on using them in the (near) future.