Twitter seems to have removed the new policy to ban accounts linking to competitors.

here is their page in the internet archive's wayback machine: https://web.archive.org/web/20221218183504/https://twitter.com/TwitterSupport/status/1604531261791522817

Twitter Support on Twitter

“We recognize that many of our users are active on other social media platforms. However, we will no longer allow free promotion of certain social media platforms on Twitter.”

Twitter
@brewsterkahle Account ban removed, but linking is still blocked. Possibly planned all along.

@shandrew hum.

My twitter profile has a link to mastodon, and is still visible to me: https://twitter.com/brewster_kahle

I am a small fish, so maybe this only applies to others.

Brewster Kahle (@brewster_kahle) / Twitter

Digital Librarian @internetarchive https://t.co/7ojy915Rea https://t.co/bAusgBFTtW https://t.co/c9qTQpvRsA @openlibrary @great78project mastodon: @[email protected]://t.co/7ojy915Rea

Twitter

@brewsterkahle Looks like mastodon.archive.org escaped whatever matching they are using to block the URLs. Most mastodon links get the "unsafe link" warning if you try to click on them.

If you try to add one of these urls to your profile, you get "Account update failed: Url is considered malware"