When a post gets old, instead of simply closing the discussion, send comments and trackbacks to the moderation queue. This will greatly reduce spam.
For documentation and tips, please refer to the official plugin page for <a href="http://planetozh.com/blog/archives/2005/02/02/wordpress-plugin-auto-moderate-comments/" title="Auto Moderate Comments" rel="nofollow ugc">Auto Moderate Comments</a>

Ozh' Auto Moderate Comments

When a post gets old, instead of simply closing the discussion, send comments and trackbacks to the moderation queue.

tempor

This plugin removes the unobtrusive footer text installed by “Ozh Admin Drop Down Menu” in the backend (admin) of wordpress.

Remove Ozh unobstrusive credits in footer

It still works with at least wordpress 4.9.3 version.

Great!

Removes Ozh footer text from the admin backend. Author: Polemos

Ozh' Auto Moderate Comments vs Remove Ozh unobstrusive credits in footer