BuddyPress.org

I provided a link to show you how to find the filter hooks for any of the functions that you listed. You use them like any other WP filter hook.
For example:

function mitchellbc_bp_get_message_thread_from( $from ) {

    // manipulate $from however you want
    $from = '<span class="text">' . $from .  '</span>'; 

    return $from; 
}
add_filter( 'bp_get_message_thread_from', 'mitchellbc_bp_get_message_thread_from', 1, 1 );