It also ridded the show of its biggest drag: Pitt's neurasthenic qualities as an actor were well-marshalled in the service of a haunted character, but he wasn't much fun. In fact, it's arguable that Jimmy Darmody's most valuable contributions to "Boardwalk Empire" were made posthumously -- that his hovering ghost gave season three the sort of little poetic shivers required to offset its more blunt-force maneuvers. At least two major characters -- Richard and Gillian -- spent the entire season reckoning with his departure; the former by avenging his friend's death by killing Manny Horovitz (William Forsythe) and then by trying to pick up his fatherly mantle with regards to little Tommy; the latter by sinking even deeper into murderous, self-pitying depression and then seeking out a Jimmy lookalike to seduce and murder in a surpassingly creepy act of maternal catharsis. (Gillian's reinvention as a surreptitious poisoner may have been an homage to Patricia Quinn's Livilla on "I, Claudius" -- who was of course famously an influence on Livia's character on "The Sopranos").
Jimmy was also definitely there in the grinning, cocksure face of Rowland Smith (Nick Robinson), the resourceful teenager capped by Nucky in "Blue Bell Boy" -- a vicious and excessive act of self-preservation that was redundant by design. Nucky's execution of Jimmy was definitive proof that he was more than "half a gangster" (another Harrow-ing proposition); killing Rowland, who had previously stolen from him but then balanced the scales by helping him hide out from the feds in a dingy basement while providing excellent company besides, indicated that what was once an agonizing process had become as easy as muscle memory.
It took "The Sopranos" until its second-to-last episode for Chase to show his hand and imply -- through his perennial audience surrogate Dr. Melfi (Lorainne Bracco) -- that any reasonable person (i.e. the audience) should give up on Tony's chances for any sort of redemption. "Boardwalk Empire" seems to be there already with regards to Nucky, whose entreaties to his newly estranged wife about financial security trumping her hatred and contempt for the man she was about to walk out on seemed to fall on deaf ears.
Except, as another former half-gangster so famously put it, just when you think you're out, you can be pulled back in. There's little doubt that Margaret Schroeder (Kelly Macdonald) will come back next year (whether crawling or on a newly acquired high horse is uncertain), and that other characters who seem to have either extricated themselves from trouble, like Eli (newly re-installed as Nucky's iron-fist-in-velvet-glove-right-hand-man), left for dead like Gillian (who is too good a distaff foil for the mostly male cast to be discarded) or else abandoned by the showrunners altogether (Michael Shannon must be filming a lot of other movies right now) will be back in trouble soon enough. Such are the dictates of serialized melodrama, which thrives on just this sort of narrative gold-bricking.
The question is whether "Boardwalk Empire" will need to engineer another fly in the ointment on the order of Gyp Rosetti -- a ridiculous character given more humour and gravitas than he probably deserved by Cannavale -- in order to keep things buzzing along. If Nucky is sincere in his desire to drop out of the public view (understandable for a guy who spent a lot of time worried that he'd be shot on sight) then maybe "Boardwalk Empire" will let somebody else assume center stage: it would be especially bold if it was the one guy left standing whose path doesn't have to tiptoe around matters of public record. Richard Harrow, come on down -- you're the best character on the most intermittently remarkable drama on television.