[asbrown]

i know this thread is ancient but I needed the same thing so heres some code if you need it as well

<?php
/*
Plugin Name: BuddyPress change last initial
Plugin URI: http://wpfixr.com
Description: Change the last name to use only the first initial
Author: Anthony Brown
Version: 1.0.0
Author URI: http://wpfixr.com
*/
$changeLastInitial = new changeLastInitial;
add_filter('bp_displayed_user_fullname', array(
    $changeLastInitial,
    'last_initial'
), 7, 1);
add_filter('bp_get_member_name', array(
    $changeLastInitial,
    'last_initial'
), 7, 1);
add_filter('bp_get_the_profile_field_value', array(
    $changeLastInitial,
    'last_initial_xprofle'
), 7, 3);
add_filter('bp_core_get_user_displayname', array(
    $changeLastInitial,
    'bp_core_get_user_displayname'
), 7, 2);

class changeLastInitial
{
    function bp_core_get_user_displayname($name, $id)
    {
        $name = $this->last_initial($name);
        return $name;
    }
    function last_initial_xprofle($value, $type, $id)
    {
        if ($id == 1) {
            $value = $this->last_initial($value);
        }
        return $value;
    }
    function last_initial($name)
    {
        $name_a = explode(' ', $name);
        // if there is at least two parts to the name
        if (count($name_a) == 2) {
            // replace the last part of the name with the first letter of the last part
            $name_a[count($name_a) - 1] = substr($name_a[count($name_a) - 1], 0, 1);
            // put it all back together
            $name  = implode(' ', $name_a);
        }
        return $name;
    }
}
?>