I've been playing in and observing chess events of all sorts and levels for 35 years, and have read about dozens, probably even hundreds of other matches and tournaments from the present going back more than 100 years before my birth. In all that time and in all my experience, both firsthand and secondhand, I've never heard of anything like what happened in round 9 of the U.S. Championship.
What happened? Wesley So was forfeited after just six moves of his game against Varuzhan Akobian for writing notes to himself on a separate piece of paper under his scoresheet. That this is forbidden is known to the overwhelming majority of amateur players; it's almost inconceivable that a professional wouldn't know this - especially a player (who was) in the world's top ten. Stranger yet, So had already been warned twice about this earlier in the tournament by Chief Arbiter Tony Rich, and his doing it a third time led to his forfeiting the game. Apparently he was only jotting down words of self-encouragement and advice, e.g. to double-check his variations, but it's against the rules of chess all the same.
So was not born in the U.S. and presumably isn't a native English speaker, but his grasp of the language is more than sufficient to understand the arbiter's earlier warnings. Clearly there's more to the story, and it is alleged in this article (HT: Allen Becker) that So has been suffering psychological pressure from his family and perhaps from Webster University's Paul Truong as well. Let's hope for his sake as a human being first and as a chess player second that he can work through those problems and find stability in his personal life. As for the rest of the championship, hopefully he can get through it without any further incidents and get his world back in order.
As for the chess, Hikaru Nakamura maintained his half-point lead over Ray Robson leading into their head-to-head matchup on Saturday. Nakamura was surprised when Timur Gareev met 1.Nf3 with 1...b6, but despite having played Owen's Defense hundreds of times in blitz on the black side he didn't handle it very well with the white pieces. Nakamura was worse, and was a bit fortunate that Gareev grabbed a second pawn and allowed Nakamura to force a draw by repetition. Robson also drew, with Black in a Scheveningen Sicilian against Sam Sevian. In fact, all the players anywhere near the lead (except for So) drew their games; the only win involving chess moves occurred in the game Daniel Naroditsky vs. Conrad Holt. Naroditsky played very well, and won his first game of the event.
In the women's section, Irina Krush has caught up to Katerina Nemcova with two rounds to go; they'll play in the last round. Krush had some enduring pressure against Tatev Abrahamyan, but the game was headed for a draw until Abrahamyan played 34...b3?, which lost. (Instead 34...Qc1, both allowing the queen to defend and to give some annoying checks, or 34...h6 to give Black's king a flight square, would have kept full equality.) Krush found a very nice and precise series of moves to win, including the easily missed 38.Qe5+. Meanwhile, Nemcova was better for much of her game with Viktorija Ni, but it never reached decisive proportions and the game was eventually drawn. Paikidze is a point back after beating Yu, and plays Nemcova in round 10. Nemcova will have White, while Krush will have Black against Yu. In the last round Krush has the white pieces vs. Nemcova, so since Krush is a huge favorite against Yu in round 10 Nemcova will have to push very hard for a win against Paikidze to maintain a reasonable chance of winning the tournament.