We'll create fresh WordPress site with Remove "Comments are closed" installed. You have 20 minutes to test the plugin after that site we'll be deleted.
On posts where comments are closed, the plugin will remove the text ‘Comments are closed.’ The plugin supports any languages/text domain, and will remove the text from themes and plugins.
Prerequisite: Since the plugin is filtering gettext, your theme/plugin must be localized.
View the plugin source code at the plugin home page