Innistrad: Midnight Hunt has seen its first banning, with a reprint of a particularly powerful artifact being booted from the Magic the Gathering Arena-exclusive Brawl and Historic Brawl formats.
Pithing Needle is an one generic mana colourless artifact that allows you to name a card. Cards with that name can't use any activated abilities (unless they just produce mana). It's easy to see where this is going: cast Pithing Needle, name your opponent's Commander. They can no longer use any of their Commander's activated abilities, which shuts down a lot of decks in the format.
While the ban has apparently been in affect since the launch of Midnight Hunt, players only noticed it when the Wizards of the Coast Support account tweeted out an announcement for it a few weeks later. This makes Pithing Needle the dubious distinction of being the first card from Midnight Hunt that has been banned in any format it otherwise would have been legal in.
Brawl is a one-vs-one format that borrows a lot from the ever-popular Commander. Decks (60 in Brawl, 100 in Historic Brawl, and only one copy of each non-basic land card) are built around an specific Legendary creature, and all cards must be within the colour identity of that Commander. Cards that can 'turn off' an opponent's Commander make up the bulk of the Brawl banlist, with Runed Halo, Drannith Magistrate and Sorcerous Spyglass all also being barred from the format.
While these cards are allowed in Commander, the format on which Brawl is based, Commander has a much bigger card pool, and also has more players who could draw into a solution to deal with them. With Pithing Needle, there is a greater chance that somebody at the table is running some kind of artifact destruction. In Brawl, someone playing a mono-black deck, which has very few viable tools for it, could have their deck completely derailed from turn one.
Other than Pithing Needle, Innistrad: Midnight Hunt so far seems to be a relatively inoffensive set. In fact, it's actually provided solutions for some of cards from other recent sets that have been causing concern, such as the introduction of Field of Ruin into Standard to counteract the Book of Exalted Deeds and Faceless Haven guaranteed win combo.
This year's been a big one for bannings in Magic, with the most recent being the surprise ban of Golos, Tireless Pilgrim in the Commander format.