Actually Alan is more or less correct here, at least in a general sense. Allied listeners (and presumably Axis as well) understood that the "style" and language of a given message was pertinent to the accuracy or content therein. Understanding who was sending the message offered clues and context to the content, which in turn added another layer to the understanding that could be derived from the received messaging.
I have seen a couple of movies, well I have see more than a couple of movies, but I remember two movies in particular, but only generally, one was a WWII submarine movie that I could probably find the name of if I looked, I don't remember the title because it was German with English subtitles, and even if I did remember the title I couldn't spell it, in which the British captured one of the German enigma machines, and another movie about the British code breakers at Bletchley, starring that guy whose last name is Cumberbatch or something similar, and both of them said that the British, mostly women I guess, who would monitor the wireless could identify the German wireless guys by their cadence when operating their telegraph keys, and that gave them clues about the content of the message. Of course they had to turn a perfectly good spy movie into a movie about being homosexual in the 1940s as if they didn't have enough material about breaking German codes and needed something else to fill out the allotted time. I am surprised nobody mentioned it yet, and here when I say "it" I mean about breaking the enigma code not the homosexual angle. Maybe you guys ought to start watching more movies. Some of the stuff in movies is true if you watch the right kind of movies. I also know that because I remember reading more than a few books about the subject, but I'm not likely to remember the titles of those either. It is hard to look up the titles of books you once read, but movies are a different story altogether.
I have no doubt that software coders have signature styles. That seems almost like a duh to me. And whoever, maybe it was John, said that you can read a book ostensibly written by some famous guy like Tom Clancy, but it is really written by his protégé or whatever, well you don't have to finish the first page to know it is a fake Clancy novel, which is a little bit of a letdown because you have only read the first page and you know it is not going to be as good, no matter how talented the protégé is. So while I think some [pick your favorite country] guy could do a pretty good imitation of a Russian code writing hacker or whatever, it would be an imitation and not a replication, and so the guys on the other side would know that and not fail for that old fake out move. Of course some conspiracy theory guys like to think up conspiracy theories where one side falls for the fake out move, but unless you are a halfwit, you know they are not true. Generally, if you make up a conspiracy theory, you want to make it at least somewhat plausible so readers don't start rolling their eyes too soon as you are explaining it. Generally.