Earlier quoted context omitted.
The surveillance, including the mass surveillance of the communication, existed even in older times. It is, for example, documented that both British and US secret services went through all the telegrams that passed their commercial infrastructure, often based on a simple "gentleman's agreement" with the companies, even in the 19th century, and certainly in the 20th. Other countries were somehow aware of that weaknes…
Back in the age of feudalism the holy roman emperor, who was neither holy, nor roman, nor an emperor, but the head of the House of Habsburg, gave the monopoly of postal services as an hereditary title to the House of Thurn und Taxis who had been building their postal services for two centuries, eliminating their competition in the empire, under the rule that letters are read and checked for conspiracy against the cro…
It's a trope that "sounds good" but IMHO doesn't get one more knowledge.
a) It was de facto an empire, but with an emperor allowing huge independence to the local rulers. So he was an emperor, even if he couldn't do "anything anytime".
"The power of the emperor was limited, and while the various princes, lords, bishops, and cities of the empire were vassals who owed the emperor their allegiance, they also possessed an extent of privileges that gave them de facto independence within their territories. " (1)
b) It was "holy" in the sense of "Christian" and in the sense of getting weaker due to the "holy wars" raging even between the parts of the empire.
c) the "roman" could be the most disputed, but it reflects the millenniums-long belief of what the "real" empire is supposed to be, namely, the one that is the successor of the rulers by which we name two months in a year even today.
The trope's origin is Voltaire. His influence on the beliefs of the western world must be acknowledged, but it must be recognized that he wrote a lot with the intention of changing them (and some changes were even bigger than he accepted).
As I write this I still haven't read https://doi.org/10.7245/0026-2005-42.1.60 but I'd expect that it worth a read for those interested in more details:
"For the historian, Voltaire's famous quip has three aspects: 1) What did Voltaire mean by it in 1756 when he wrote the line in his Essay on Customs? 2) How did contemporaries, including the Austrian Habsburgs, understand it? 3) Does the quote accurately describe the events the Philosophe is discussing (Charles IV of Bohemia and the Golden Bull of 1356)? Voltaire in fact exaggerates the weakness of the Empire in both 1356 and 1756, and uses an anachronistic standard to evaluate both: the quasi nation states of the 1750s. The three parts of the imperial title had changed in meaning during the four centuries after 1356. The jibe nonetheless reflects something of the thought of Voltaire and the French Enlightenment."