hashbuddy fix suggestion in reply to https://buddypress.trac.wordpress.org/ticket/5786

gistfile1.php

<?php
/**
 * NB: Since 2.1 beta 1
 *
 * Activity Load Newest & Loadmore feature will transport
 * search terms through ajax.
 *
 * @see  https://buddypress.trac.wordpress.org/changeset/8817
 */
function hashbuddy_activity_hashtags_querystring( $query_string, $object ) {
	// i think there's no need to get $bp global
	// global $bp;

	// Bail if not an activity query string
	if ( 'activity' != $object ) {
		return $query_string;
	}

	// put query string into an array
	$hashbuddy_query_string = wp_parse_args( $query_string, array() );

	$pattern = '/[#]([\p{L}_0-9a-zA-Z-]+)/iu';

	// Try the $_GET var (the 's' one as the 'hash' one doesn't exist in the url)
	// this will only work on page load
	if ( ! empty( $_GET['s'] ) && preg_match( $pattern, $_GET['s'] ) ) {
		// Populate search terms
		$hashbuddy_query_string['search_terms'] = $_GET['s'];

		// Plugin is forcing comments to also have their own activity
		$hashbuddy_query_string['display_comments'] = true;

		// Override the query string
		$query_string = $hashbuddy_query_string;
	}

	return $query_string;

	/*
	Original code

	if ( isset( $_GET['hash'] ) ) {

		$hash = $_GET['hash'];

	// Now pass the querystring to override default values.
	$query_string .= '&display_comments=true&search_terms=#' . $hash;

	}

	return $query_string;*/
}
add_filter( 'bp_ajax_querystring', 'hashbuddy_activity_hashtags_querystring', 11, 2 );
add_filter( 'bp_dtheme_ajax_querystring', 'hashbuddy_activity_hashtags_querystring', 11, 2 );