Hi Daniel,
Thank you for the question.
If you do not want to use translation, you will need to override template if using legacy template pack.
Please copy parent-theme/buddypress/activity/post-form.php (if not present, you will need to copy it from plugin/buddypress/bp-templates/bp-legacy /buddypress/activity/post-form.php
If you are using BP Nouveau, the above method will not work.
you can use the following code in bp-custom.php or functions.php of your theme
add_filter( 'bp_core_get_js_strings', function ( $params ) {
if ( ! isset( $params['activity'] ) || ! isset( $params['activity']['strings'] ) ) {
return $params;
}
$params['activity']['strings']['whatsnewPlaceholder'] = sprintf( __( "Hello, What's new, %s?", 'buddypress' ), bp_get_user_firstname( bp_get_loggedin_user_fullname() ) );
return $params;
}, 100 );
Regards
Brajesh