Update: A Valve representative has confirmed via email that Portal 2 co-writer Jay Pinkerton has returned to the company. Read the original story below for more details.
Portal 2 co-writer Jay Pinkerton appears to have returned to Valve, a year after he left the company.
2017 saw an exodus of Valve writers: Erik Wolpaw and Chet Faliszek, who wrote Portal 2 alongside Pinkerton, left in February and May respectively, and Pinkerton followed suit in June.
As well as Portal 2, Pinkerton wrote parts of Left 4 Dead and Left 4 Dead 2, as well as a lot of the ancillary stuff surrounding Valve's games, such as the TF2 comics.