After having left a year ago, a Valve representative has confirmed via email that Portal 2 co-writer Jay Pinkerton has returned to the company.
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.
Source: N4G PC Portal 2 co-writer Jay Pinkerton returns to Valve