Michael Torbert

This plugin is great for someone needing to debug their own or another person’s WordPress site. It will collect and display and/or send debug information to an email address provided by the user. 
This is helpful for plugin or theme authors wanting to debug user’s sites.
Some features:
<ul>
<li>Displays system information</li>
<li>Emails system information</li>
</ul>
<h3>Arbitrary section</h3>
You may provide arbitrary sections, in the same format as the ones above. This may be of use for extremely complicated 
plugins where more information needs to be conveyed that doesn’t fit into the categories of “description” or 
“installation.” Arbitrary sections will be shown below the built-in sections outlined above.
<h3>A brief Markdown Example</h3>
Ordered list:
<ol>
<li>Some feature</li>
<li>Another feature</li>
<li>Something else about the plugin</li>
</ol>
Unordered list:
<ul>
<li>something</li>
<li>something else</li>
<li>third thing</li>
</ul>
Here’s a link to <a href="https://wordpress.org/" title="Your favorite software" rel="ugc">WordPress</a> and one to <a href="http://daringfireball.net/projects/markdown/syntax" title="Markdown is what the parser uses to process much of the readme file" rel="nofollow ugc">Markdown’s Syntax Documentation</a>. 
Titles are optional, naturally.
Markdown uses email style notation for blockquotes and I’ve been told:
<blockquote>
Asterisks for emphasis. Double it up for strong.
</blockquote>
<pre><code><?php code(); // goes in backticks ?>
</code></pre>

WordPress Debug

Displays and emails system information for debugging purposes for easy debugging of your own or a client/user site.

JS Morisset

The JSM Show User Metadata plugin displays user profile meta keys and unserialized values in a metabox at the bottom of the user profile editing page.
There are no plugin settings – simply install and activate the plugin.
<h4>Available Filters for Developers</h4>
Filter the user meta shown in the metabox:
<pre><code>'jsmsum_metabox_table_metadata' ( array $metadata, $user_obj )
</code></pre>
Array of regular expressions to exclude meta keys:
<pre><code>'jsmsum_metabox_table_exclude_keys' ( array $exclude_keys, $user_obj )
</code></pre>
Capability required to show user meta:
<pre><code>'jsmsum_show_metabox_capability' ( 'manage_options', $user_obj )
</code></pre>
Show user meta for a screen base (defaults to true):
<pre><code>'jsmsum_show_metabox_screen_base' ( true, $screen_base )
</code></pre>
Capability required to delete user meta:
<pre><code>'jsmsum_delete_meta_capability' ( 'manage_options', $user_obj )
</code></pre>
Icon for the delete user meta button:
<pre><code>'jsmsum_delete_meta_icon_class' ( 'dashicons dashicons-table-row-delete' )
</code></pre>
<h4>Related Plugins</h4>
<ul>
<li><a href="https://wordpress.org/plugins/jsm-show-comment-meta/" rel="ugc">JSM Show Comment Metadata</a></li>
<li><a href="https://wordpress.org/plugins/jsm-show-order-meta/" rel="ugc">JSM Show Order Metadata for WooCommerce HPOS</a></li>
<li><a href="https://wordpress.org/plugins/jsm-show-post-meta/" rel="ugc">JSM Show Post Metadata</a></li>
<li><a href="https://wordpress.org/plugins/jsm-show-term-meta/" rel="ugc">JSM Show Term Metadata</a></li>
<li><a href="https://wordpress.org/plugins/jsm-show-user-meta/" rel="ugc">JSM Show User Metadata</a></li>
<li><a href="https://wordpress.org/plugins/jsm-show-registered-shortcodes/" rel="ugc">JSM Show Registered Shortcodes</a></li>
</ul>

JSM Show User Metadata

throws now errors/warnings, good performance, just fulfills it's job. 5 stars

just works

Show user metadata in a metabox when editing users - a great tool for debugging issues with user metadata.

WordPress Debug vs JSM Show User Metadata