[@robin-w Moderator 8 years, 5 months ago]

This can be done, but requires you to be able to use FTP and edit a file

create a directory on your theme called ‘bbpress’
ie wp-content/themes/%your-theme-name%/bbpress

where %your-theme-name% is the name of your theme

find
wp-content/plugins/bbpress/templates/default/bbpress/content-statistics.php
Make a copy of this file, and put in in the directory called bbpress that you created above, so you end up with
wp-content/themes/%your-theme-name%/bbpress/content-statistics.php
bbPress will now use this template instead of the original
and you can amend this.

so open the file and you will see starting at line 17

<dt><?php _e( 'Registered Users', 'bbpress' ); ?></dt>
	<dd>
		<strong><?php echo esc_html( $stats['user_count'] ); ?></strong>
	</dd>

remove this and save the file back to wp-content/themes/%your-theme-name%/bbpress/content-statistics.php