In the U.S., requiring a login (or any information other than your email address) to opt out is against the law. Additionally, you cannot require any steps other than "sending a reply electronic mail message or visiting a single Internet Web page."

I once wrote to the FTC for guidance as to whether or not this included requiring unsubscribers to solve a CAPTCHA or disable adblockers or enable Javascript, but did not get a response. I believe the law is plain with regards to this, but a lot of companies seem to be willing to risk it.

See: https://www.ecfr.gov/current/title-16/chapter-I/subchapter-C...

In this case, "null MX record" means MX exists, but does not specify a valid server:

   $ host -t mx example.com
   example.com mail is handled by 0 .

I use uBlock Origin for this, something like:

  news.ycombinator.com##:matches-path(/^/item\?id=/) tr a.hnuser:has-text(/^dpifke$/):upward(tr)

The very first subheading is entitled "What to Submit." I quoted it in my initial reply as rationale for why the people flagging this submission as off-topic were justified.