Hi @pputzer, thank you for your reply! This is nearly unmodified. I only replaced a customer’s name with testuser1 for privacy reasons. But it’s a clear username, not a hex string. This is one line in error.log. I post more of the error log, I only change the user names:
[Wed Jul 22 20:07:31.778858 2020] [php7:notice] [pid 20096:tid 1772] [client ::1:55243] WordPress database error You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'WHERE hash = 'Gerhard C.'' at line 1 for query SELECT * FROM WHERE hash = 'Gerhard C.' made by wp_dashboard, do_meta_boxes, WC_Admin_Dashboard->recent_reviews, get_avatar, get_avatar_url, get_avatar_data, apply_filters('pre_get_avatar_data'), WP_Hook->apply_filters, Avatar_Privacy\\Components\\Avatar_Handling->get_avatar_data, Avatar_Privacy\\Components\\Avatar_Handling->should_show_gravatar, Avatar_Privacy\\Components\\Avatar_Handling->determine_gravatar_policy, Avatar_Privacy\\Core->comment_author_allows_gravatar_use, Avatar_Privacy\\Core->load_data, Avatar_Privacy\\Core->load_data_by_hash, referer: https://localhost/wp_pub/produkt/nanocul-433/
[Wed Jul 22 20:07:31.780853 2020] [php7:notice] [pid 20096:tid 1772] [client ::1:55243] WordPress database error You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'WHERE hash = 'Matthias B.'' at line 1 for query SELECT * FROM WHERE hash = 'Matthias B.' made by wp_dashboard, do_meta_boxes, WC_Admin_Dashboard->recent_reviews, get_avatar, get_avatar_url, get_avatar_data, apply_filters('pre_get_avatar_data'), WP_Hook->apply_filters, Avatar_Privacy\\Components\\Avatar_Handling->get_avatar_data, Avatar_Privacy\\Components\\Avatar_Handling->should_show_gravatar, Avatar_Privacy\\Components\\Avatar_Handling->determine_gravatar_policy, Avatar_Privacy\\Core->comment_author_allows_gravatar_use, Avatar_Privacy\\Core->load_data, Avatar_Privacy\\Core->load_data_by_hash, referer: https://localhost/wp_pub/produkt/nanocul-433/
[Wed Jul 22 20:07:31.782848 2020] [php7:notice] [pid 20096:tid 1772] [client ::1:55243] WordPress database error You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'WHERE hash = 'maxmuster9586'' at line 1 for query SELECT * FROM WHERE hash = 'maxmuster9586' made by wp_dashboard, do_meta_boxes, WC_Admin_Dashboard->recent_reviews, get_avatar, get_avatar_url, get_avatar_data, apply_filters('pre_get_avatar_data'), WP_Hook->apply_filters, Avatar_Privacy\\Components\\Avatar_Handling->get_avatar_data, Avatar_Privacy\\Components\\Avatar_Handling->should_show_gravatar, Avatar_Privacy\\Components\\Avatar_Handling->determine_gravatar_policy, Avatar_Privacy\\Core->comment_author_allows_gravatar_use, Avatar_Privacy\\Core->load_data, Avatar_Privacy\\Core->load_data_by_hash, referer: https://localhost/wp_pub/produkt/nanocul-433/
[Wed Jul 22 20:07:31.783845 2020] [php7:notice] [pid 20096:tid 1772] [client ::1:55243] WordPress database error You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'WHERE hash = 'testuser1'' at line 1 for query SELECT * FROM WHERE hash = 'testuser1' made by wp_dashboard, do_meta_boxes, WC_Admin_Dashboard->recent_reviews, get_avatar, get_avatar_url, get_avatar_data, apply_filters('pre_get_avatar_data'), WP_Hook->apply_filters, Avatar_Privacy\\Components\\Avatar_Handling->get_avatar_data, Avatar_Privacy\\Components\\Avatar_Handling->should_show_gravatar, Avatar_Privacy\\Components\\Avatar_Handling->determine_gravatar_policy, Avatar_Privacy\\Core->comment_author_allows_gravatar_use, Avatar_Privacy\\Core->load_data, Avatar_Privacy\\Core->load_data_by_hash, referer: https://localhost/wp_pub/produkt/nanocul-433/
I think the code is called in woocommerce single-product-reviews.php with those lines:
<ol class="commentlist">
<?php wp_list_comments( apply_filters( 'woocommerce_product_review_list_args', array( 'callback' => 'woocommerce_comments' ) ) ); ?>
</ol>
Please tell me what else do you need to find out what causes this?