$wpdb bug with PHP > = 8?

For a long time, I’ve been using a function to filter user’s comments and add some information, like their roles and number of comments on my site. It’s working okay with PHP < 8, but after updating to any version >= 8, it returns a strange result. Is there any known bug/incompatibility of wpdb with version 8 of php?

Example: inside my function, this is the result of $wpdb in PHP 7:

wpdb Object
(
[show_errors] =>
[suppress_errors] =>
[last_error] =>
[num_queries] => 145
[num_rows] => 0
[rows_affected] => 0
[insert_id] => 0
[last_query] => SELECT * FROM wp_users WHERE user_email = '[email protected]' LIMIT 1
[last_result] => Array

etc...

So this way, I can get comment user’ ID and do my stuff, like this:

$comm_count = $wpdb->get_var('SELECT COUNT (comment_ID) FROM ' . $wpdb->comments. ' WHERE comment_author_email = "' . get_comment_author_email() . '"');

But with PHP 8, this is happening:

wpdb Object
(
    [show_errors] => 
    [suppress_errors] => 
    [last_error] => 
    [num_queries] => 132
    [num_rows] => 0
    [rows_affected] => 0
    [insert_id] => 0
    [last_query] => SELECT * FROM wp_users WHERE user_login = '#' LIMIT 1
    [last_result] => Array

etc...

The query goes from user_email to user_login, any clue why?