functions.php

add_action('amp_post_template_css', function () {
    ?>
    .amp-wp-article-footer .amp-wp-meta {
        display: block;
    }

    .amp-wp-comments-link a {
        border-style: solid;
        border-color: #c2c2c2;
        border-width: 1px 1px 2px;
        border-radius: 4px;
        background-color: transparent;
        color: #0a89c0;
        cursor: pointer;
        display: block;
        font-size: 14px;
        font-weight: 600;
        line-height: 18px;
        margin: 0 auto;
        max-width: 200px;
        padding: 11px 16px;
        text-decoration: none;
        width: 50%;
        -webkit-transition: background-color .2s ease;
        transition: background-color .2s ease;
        text-align: center;
    }
    <?php
},99999);