Sorry, just to clarify, I was looking for an example of the fep_filter_read_receipt filter in use as I couldn’t decipher it from the core code to make customisations.

So this will filter the name and date, time.

add_filter( 'fep_filter_read_receipt_individual', function( $receipt, $time, $participant ){
    if ($time > strtotime('-1 day')) {
		$time = sprintf( __( '%s', 'front-end-pm' ), date("G:i", $time) );
		// $time = sprintf( __( '%s ago', 'front-end-pm' ), human_time_diff($time) );
	} elseif ($time > strtotime('-6 day')) {
		$time = sprintf( __( '%s', 'front-end-pm' ), date("D G:i", $time) );
	} else { 
		$time = sprintf( __( '%s', 'front-end-pm' ), date("j M Y, G:i", $time) );
	}
	return '<b>Read</b> ' . $time;
}, 10, 3);

// Read 21:18

How do I filter out the <hr /><div class=”fep-read-receipt”>…</div>?

This was what I came up with before you pointed me towards the _individual filter…

add_filter( 'fep_filter_read_receipt', function(){	
	$participants = FEP_Participants::init()->get( fep_get_the_id(), false, true );
	$time = array();
	foreach ( $participants as $participant ) {
		if ( ! $participant->mgs_read ) {
			continue;
		}
		if ( fep_get_message_field( 'mgs_author' ) == $participant->mgs_participant ) {
			continue;
		}
		$time = $participant->mgs_read;
	}
	return 'Read ' . date('G:i', $time);
}, 10, 2);

But I know that’s not the right way to do it. I’m still trying to feel my way through the plugin, but getting there.

It’s easy when you know how. Much appreciated.

Final code in my front-end-pm-mod plugin.

add_filter( 'fep_filter_read_receipt_individual', function( $receipt, $time, $participant ){
    if ($time > strtotime('-1 day')) {
    	$time = sprintf( __( '%s', 'front-end-pm' ), date("G:i", $time) );
		// $time = sprintf( __( '%s ago', 'front-end-pm' ), human_time_diff($time) );
	} elseif ($time > strtotime('-6 day')) {
		$time = sprintf( __( '%s', 'front-end-pm' ), date("D G:i", $time) );
	} else { 
		$time = sprintf( __( '%s', 'front-end-pm' ), date("j M Y, G:i", $time) );
	}
	if ( $participant == get_current_user_id()) {
		return '';
	} else {
		return '<div class="fep-msg-read fep-msg-read-pad"><b>Read</b> ' . $time. '</div>';
	}
}, 10, 3);

add_filter( 'fep_filter_read_receipt', function( $output, $receipt ){
	return implode( '', $receipt );
}, 10, 2);

And in related to the other question I asked, how do I get the recipient name (To:). This was as part of a custom template version of veiw-message-content.php.

echo '<div class="fep-msg-author"><b>' . fep_user_name( fep_get_message_field( 'mgs_author' ) ) . '</b></div>';
			$recipients = fep_get_participants( fep_get_the_id( $mgs_id ) );
			foreach ( $recipients as $recipient ) {
				if( fep_get_message_field( 'mgs_author', $mgs_id ) != $recipient )
				echo '<div class="fep-msg-recipient">to ' . fep_user_name( $recipient ) . '</div>';
			}