Yahoo! JAPAN changed its comment policy in order improve user safety and convenience, as well as to strengthen the prevention of inappropriate comments.
After November 15, 2022, if you are logged in Yahoo Japan without attaching Japanese mobile number, you won’t be able to posting comments.
Source: https://news.yahoo.co.jp/newshack/information/comment_SMSauth_20221018.html
https://www.reddit.com/r/japan/comments/yshqtq/yahoo_japan_comment_policy_update_mandatory/