<p>This plugin will integrate AJAX commenting feature into your WordPress Blog. It uses the powerful JavaScript Framework jQuery to handle AJAX requests and jQuery Validation plugin by bassitance.de to validate comment form on the client side.</p>
<h4>Feature Summary</h4>
<ul>
<li>Enable AJAX Commenting</li>
<li>Client Side Form Validation</li>
<li>Easily rolls back if JS disabled</li>
<li>Easily configure custom styles for messages</li>
</ul>
<p><strong><a href="http://webdeveloperplus.com/wordpress/new-wordpress-plugin-wdp-ajax-comments/" rel="nofollow ugc">See plugin page for more details</a></strong></p>


WDP AJAX Comments

This plugin will enable AJAX comment posting on your WordPress blog.

Miguel Useche

<p>This plugin provides a widget and a filter to display a collapsible list of categories in your sidebar or posts by using vanilla Javascript.</p>
<h4>Features</h4>
<ol>
<li>Support for Gutenberg blocks. Add it to any FSE theme or Gutenberg compatible theme.</li>
<li>Display a collapsed list of your archives to reduce space.</li>
<li>Uses vanilla JS to add effects and to be compatible with all browsers.</li>
<li>Select the symbol for expanding/collapsing categories</li>
<li>Select categories to exclude, so it shows only the categories you want.</li>
<li>Autoexpand selected category (including it parent or child).</li>
<li>Support for multiple instances.</li>
<li>Simple layout configuration</li>
<li>Shortcode support  <em>[JsCategoriesList]</em></li>
<li>Translated to Spanish, Italian Russian, Slovak, Czech.</li>
<li>Compatible with most JS cache and minify plugins.</li>
<li>And more to come…</li>
</ol>
<h3>Configuration</h3>
<ul>
<li>Title: title of the widget.</li>
<li>Trigger Symbol:  characters to be displayed as a bullet.</li>
<li>Symbol position: where to put the expand/collapse symbol.</li>
<li>Effect: JS’s effect to use.</li>
<li>Order by: display order of categories.</li>
<li>Expand: if list should be expanded or callapsed by default.</li>
<li>Show number of posts: display how many post are published in the category.</li>
<li>Show empty categories: display categories with no posts.</li>
<li>Open links in a new page: render category links with target=”_blank”.</li>
<li>Categories to include: categories to be included from the list.</li>
<li>Categories to exclude: categories to be excluded from the list.</li>
</ul>


JS Categories List Widget

Haven't seen any problems running this with WordPress 4.9.8, even though it's marked as untested for a long time.  It must have been well written.

Works well with 4.9.8

A simple Gutenberg block and JS widget (can be called from posts) for displaying categories in a list with some effects.

WDP AJAX Comments vs JS Categories List Widget