How to disable ALL comments.

Have you tried:

– deactivating all plugins to see if this resolves the problem. If this works, re-activate the plugins one by one until you find the problematic plugin(s).

– switching to the Twenty Ten theme to rule out any theme-specific problems.

– resetting the plugins folder by FTP or PhpMyAdmin. Sometimes, an apparently inactive plugin can still cause problems.

There used to be an option in each post on whether to allow comments or not, but with the updated versions, it’s not there.

click ‘screen options’ near the top right of the ‘edit post’ and ‘edit page’ pages;

then tick the ‘discussion’ box;

then check again below the post/page editor, to hopefully find the ‘discussion’ area.
enable/disable the comments there.

… in case you’ll struggle:

UPDATE wp_posts SET comment_status='closed' WHERE post_date<'2011-05-01 00:00:00'

click ‘screen options’ near the top right of the ‘edit post’ and ‘edit page’ pages;

then tick the ‘discussion’ box;

then check again below the post/page editor, to hopefully find the ‘discussion’ area.
enable/disable the comments there.

You’re amazing! This worked. Thank you!