Correct return value for comment_exists(). fixes #20494.

git-svn-id: http://core.svn.wordpress.org/trunk@23433 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Fix typos in phpdoc. props markmcwilliams. fixes #23481.

git-svn-id: http://core.svn.wordpress.org/trunk@23434 1a063a9b-81f0-0310-95a4-ce76da25c4cd