BuddyPress.org

Edit timed out on me up there and didn’t get to revise my reply in time!

/buddypress/activity/post.form.php, overload it child theme

/*
 * Template tag to prepare the activity post form checks capability and enqueue needed scripts.
 */

if( bp_is_group() && !current_user_can('administrator') ) {

} else {

bp_nouveau_before_activity_post_form();
?>

<h2 class="bp-screen-reader-text"><?php echo esc_html_x( 'Post Update', 'heading', 'buddypress' ); ?></h2>

<div id="bp-nouveau-activity-form" class="activity-update-form"></div>

<?php
/*
 * Template tag to load the Javascript templates of the Post form UI.
 */
bp_nouveau_after_activity_post_form();

}