Hook in custom fields in 'about yourself' for edit user profile page

I find it amazing that the documentation for this particular area is lacking so much. This is what I found out which I guess the same as you figured out based on your question.

We can easily add fields to the contact info like so

//modify contact info
function modify_contact_methods($profile_fields) {

	// Field addition and removal will be done here
            $profile_fields['facebook'] = 'Facebook Address';

	    return $profile_fields;
}
add_filter('user_contactmethods', 'modify_contact_methods');

If we want to add fields to the about yourself section and not in an additonal section we have to do dum hackery like:

function move_shit_around() {
    ?>
    <script type="text/javascript">
        jQuery(document).ready(function($) {
            field = $('#custom_user_field').remove();
            field.insertBefore('#password');
        });
    </script>
    <?php
}
add_action( 'admin_head', 'move_shit_around' );

I found some action hooks but I have not been able to get them to work properly: https://codex.www.ads-software.com/Plugin_API/Action_Reference/show_user_profile

also the section is incomplete. If you can make it work please share since I am on the lookout for the same solution as you. Filters and hooks no hacks!

So my solution so far is this. NOTE that it uses jquery to move stuff around. And while it works the custom profile field is always empty, Even though the content is saved ??

functions.php

//modify about yourself
function add_custom_user_profile_fields( $user ) {
?>
    <table id="custom_user_field_table" class="form-table">
        <tr id="custom_user_field_row">
            <th>
                <label for="specs"><?php _e('Anl?gsspecifikationer', 'your_textdomain'); ?></label>
            </th>
            <td>
                <textarea rows="5" name="specs" id="specs" value="<?php echo esc_attr( get_the_author_meta( 'specs', $user->ID ) ); ?>" class="regular-text" ></textarea><br />
                <span class="description"><?php _e('Share your sound system specs here', 'your_textdomain'); ?></span>
            </td>
        </tr>
    </table>
<?php
}
add_action( 'show_user_profile', 'add_custom_user_profile_fields' );
add_action( 'edit_user_profile', 'add_custom_user_profile_fields' );

function move_shit() {
    $screen = get_current_screen();
    if ( $screen->id != "profile" && $screen->id != "user-edit" )
        return;
    ?>
    <script type="text/javascript">
        jQuery(document).ready(function($) {
            field = $('#custom_user_field_row').remove();
            field.insertBefore('#password');
        });
    </script>
    <?php
}
add_action( 'admin_head', 'move_shit' );

add_action('edit_user_profile', 'add_extra_profile_fields');

add_action('show_user_profile', 'add_extra_profile_fields');

//////////
function fb_save_custom_user_profile_fields( $user_id ) {

	if ( !current_user_can( 'edit_user', $user_id ) )
		return FALSE;

	update_usermeta( $user_id, 'specs', $_POST['specs'] );
}

add_action( 'show_user_profile', 'fb_add_custom_user_profile_fields' );
add_action( 'edit_user_profile', 'fb_add_custom_user_profile_fields' );

add_action( 'personal_options_update', 'fb_save_custom_user_profile_fields' );
add_action( 'edit_user_profile_update', 'fb_save_custom_user_profile_fields' );
////////////

then in the theme add (ie. author.php)

<?php $profileStuff = (get_query_var('author_name')) ? get_user_by('slug', get_query_var('author_name')) : get_userdata(get_query_var('author')); ?>
<?php echo $profileStuff->specs; ?>

Change this

<textarea rows="5" name="specs" id="specs" value="<?php echo esc_attr( get_the_author_meta( 'specs', $user->ID ) ); ?>" class="regular-text" ></textarea><br />

to this

<textarea rows="5" name="specs" id="specs" class="regular-text" ><?php echo esc_attr( get_the_author_meta( 'specs', $user->ID ) ); ?></textarea><br />

because textarea does not have a value field. It is held between the <textarea></textarea>

Now it all works but yeah, still with the minor jquery hack to move it to the right location