Excerpt, Discussion & Author boxes disappeared in Post Editing

3.1 hides some screen options on posts & pages edit screens by default. Just turn on the ones you want.
More info here: https://ottopress.com/2011/wp-quickie-metaboxes/

keesiemeijer,

THANK YOU, you just saved my Friday Morning. While I like this new functionality a lot, defaulting to SHOWING ALL would be better. and save a lot of freaking out.

Again, thank you!

a streamlined writing interface that hides many of the seldom-used panels by default to create a simpler and less intimidating writing experience for new bloggers (visit Screen Options in the top right to get old panels back),

WordPress 3.1, lots of fun

It is kinda mentioned in the release announcement…. its hard to decide what’s the best way to launch a feature I would guess… ya know?

Yes, I think so too, but they must have had good reasons to hide them by default.

Now that I am using it, it is a pretty great idea. I would default it with everything showing as usual and maybe have an alert at top of page (like the WP Latest Update alert) that says “You can now hide seldom used…”

You can show all default hidden options with this in your functions:

add_filter('default_hidden_meta_boxes', 'be_hidden_meta_boxes', 10, 2);
function be_hidden_meta_boxes($hidden, $screen) {
	if ( 'post' == $screen->base || 'page' == $screen->base )
	// $hidden = array('slugdiv', 'trackbacksdiv', 'postexcerpt', 'commentstatusdiv', 'commentsdiv', 'authordiv', 'revisionsdiv');
      $hidden = array();
      // all default hidden screen options removed
	return $hidden;
}

I have the same issue when I upgrade to version 3.1 and I found out that
its not a WordPress error or any problems with my current plugins, WordPress just hides them for some reason. I fixed it with “Screen Options”. Thank you.

Here is my case: Excerpt box disappeared on WordPress New Version