bbPress.org

Ok, you need to do the following

If you have a child theme, then do this in there

If you don’t have a child theme, then seriously consider creating one, it’s very quick and easy, and will ensure that changes you make don’t get lost on theme or bbpress upgrades. Just google wordpress child theme videos and you’ll get lots of help.

In your theme create a bbpress directory
wp-content/themes/yourthemename/bbpress

then copy

wp-content/plugins/bbpress/templates/default/bbpress/loop-single-topic.php to this directory so that you have
wp-content/themes/yourthemename/bbpress/loop-single-topic.php

Edit this file to delete line 60 which says

<span class="bbp-topic-started-by"><?php printf( __( 'Started by: %1$s', 'bbpress' ), bbp_get_topic_author_link( array( 'size' => '14' ) ) ); ?></span>

and save.

bbPress will now use the file in your theme’s bbpress folder instead of the default, and you won’t lose your change on bbpress upgrades – but will it it is in your main theme, so if you don’t create a child theme, keep a note of what you changed, as if your theme updates, then you may/will lose the bbpress folder and file.

great – glad you’re fixed