Many clues have come from Twitter accounts belonging to game devs, and from accounts that were created for the ARG. Some accounts may or may not be related to the ARG and there's no way to tell yet.
Dev Twitter accounts
Jim Crawford: @mogwai_poet
Justin Bortnick: @LordHuffnPuff
Rachel Sala: @rachel_salad
Ryan Ike: @RyanIkeComposer
Accounts created for the ARG
obeardy gnarlson: @obeardy
Michelle Obama: @flotus44
Ashby Brewery: @AshbyBrewery
RESISTANCE/PONTIFF ZAGMAR: @RESIST_DECAY
-On August 13 2016 the account was temporarily reclaimed by Pontiff Zagmar, who seems to be an enemy of the resistance that had kidnapped and imprisoned Jim Crawford. Crawford joined Zagmar's cause in exchange for freedom. The Resistance took back the account on August 15, saying that the intruders had been contained in sublevel C. See twitter profile for more details. Zagmar was previously mentioned in the Joshua/Giraffe document library.
Accounts that may or may not be part of the ARG
Is The Jig Up Yet? : @IsTheJigUpYet