Fixing bbPress 2.6 threaded (nested) replies & paging (original code [wpup.co](https://wpup.co/bbpress-threaded-nested-replies-with-paging/)) (see [bbpress forum for discusion](https://bbpress.org/forums/topic/what-is-the-status-of-threaded-nested-replies-and-pagination/#post-207457))

functions.php

<?php

//------------------------------------------------------//
// Add pagination to topics 
//------------------------------------------------------//
function wpup_bbp_list_replies($args)
{

    // Reset the reply depth
    bbpress()->reply_query->reply_depth = 0;

    // In reply loop
    bbpress()->reply_query->in_the_loop = true;

    $r = bbp_parse_args($args, array(
        'walker'       => null,
        'max_depth'    => bbp_thread_replies_depth(),
        'style'        => 'ul',
        'callback'     => null,
        'end_callback' => null
    ), 'list_replies');

    // Get replies to loop through in $_replies
    $walker = new BBP_Walker_Reply;
    $walker->paged_walk(bbpress()->reply_query->posts, $r['max_depth'], $r['page'], $r['per_page'], $r);

    bbpress()->max_num_pages = $walker->max_pages;
    bbpress()->reply_query->in_the_loop = false;
}

//Custom Pagination function
function wpup_custom_pagination($numreplies = '', $pagerange = '', $paged = '', $repliesperpage = '')
{

    /**
     * $pagerange
     * How many pages to display after the current page
     * Used in combination with 'shaw_all' => false
     */
    if (empty($pagerange)) {
        $pagerange = 3;
    }

    /**
     * $numreplies
     * What is the total number of replies in the current topic
     * $numpages
     * Calculate total number of pages to display based on number of replies and replies per page
     */
    if ($numreplies != '') {
        $numpages = ceil($numreplies / $repliesperpage);
    }

    //assign value of 1 to $paged variable in case it's not passed on 
    global $paged;
    if (empty($paged)) {
        $paged = 1;
    }

    /** 
     * We construct the pagination arguments to enter into our paginate_links
     * function. 
     */
    $pagination_args = array(
        'base'            => get_pagenum_link(1) . '%_%',
        'format'          => 'page/%#%',
        'total'           => $numpages,
        'current'         => $paged,
        'show_all'        => False,
        'end_size'        => 1,
        'mid_size'        => $pagerange,
        'prev_next'       => True,
        'prev_text'       => __('&lt;'),
        'next_text'       => __('&gt;'),
        'type'            => 'plain',
        'add_args'        => false,
        'add_fragment'    => ''
    );

    $paginate_links = paginate_links($pagination_args);

    if ($paginate_links) {
        echo "<nav class='custom-pagination'>";
        echo $paginate_links;
        echo "</nav>";
    }
}
// END Add pagination to topics -------------------------------------//

loop-replies.php

<?php
/**
 * Replies Loop
 *
 * @package bbPress
 * @subpackage Theme
 */

$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
$bbpressRepliesPerPage = 20;
?>
<div id="pagination-links">
    <?php
    // Change $bbpressRepliesPerPage to number of replies you specified in wpup_bbp_list_replies
    // First find the number of parent posts only and pass that to the custom pagination function
    $replyposts = bbpress()->reply_query->posts;
    $numparentreplies = 0;
    foreach ($replyposts as $value) {
        if ($value->reply_to == 0) {
            $numparentreplies++;
        }
    }
    wpup_custom_pagination($numparentreplies, "", $paged, $bbpressRepliesPerPage); ?>
</div>

<?php $replyposts = bbpress()->reply_query->posts; ?>

<ul id="topic-<?php bbp_topic_id(); ?>-replies" class="forums bbp-replies">

    <li class="bbp-body">
        <?php if (bbp_thread_replies()) : ?>

            <?php wpup_bbp_list_replies(array('page' => $paged, 'per_page' => $bbpressRepliesPerPage)); ?>

        <?php else : ?>

            <?php while (bbp_replies()) : bbp_the_reply(); ?>

                <?php bbp_get_template_part('loop', 'single-reply'); ?>

            <?php endwhile; ?>

        <?php endif; ?>

    </li>

</ul>
<div id="pagination-links">
    <?php
    //Change $bbpressRepliesPerPage to number of replies you specified in wpup_bbp_list_replies
    //First find the number of parent posts only and pass that to the custom pagination function
    $replyposts = bbpress()->reply_query->posts;
    $numparentreplies = 0;
    foreach ($replyposts as $value) {
        if ($value->reply_to == 0) {
            $numparentreplies++;
        }
    }
    wpup_custom_pagination($numparentreplies, "", $paged, $bbpressRepliesPerPage); ?>
</div>