What point is Orwell making about the role of communication in Soviet society with the ultimate change in the 7 commandments?
I think that Orwell is making the fundamental argument that communication and information can become tools of those in the position of power to consolidate their power. Squealer becomes the critical figure in this understanding. As Napoleon increases his hold on political authority on the farm, the rewriting of both commandments and historical narrative is a means by which he can solidify his control over the animals and ensure that his authority is legitimized. Squealer's role as the state sponsored media is essential in this process. Both Napoleon and Squealer understand that the ability to "spin" or manipulate public perception in their favor enables them to do more than if they allowed the animals to think for themselves. Orwell is suggesting that individuals have to look beyond government platitudes and information and fully understand what those in the position of power hope to gain in the attempt to gain control. In this light, communication is seen as a political element, something that directly relates to power and those who have it. It is at this point where communication becomes synonymous with propaganda.
Through the changing of the Seven Commandments, Orwell makes two points about communication in Soviet society.
Firstly, in this regime, communication becomes a tool for oppression. Notice how the Commandments are changed without any prior discussion with the other animals and without their consent. As such, Orwell highlights the relationship between language and power. The Commandments, once a symbol of freedom on the farm, are now used by the pigs as a means of social control. They give the pigs total power on the farm and, more importantly, leave the other animals helpless to change the power dynamic. Thus, language has enabled the pigs to cement their domination and absolute power.
Secondly, the changing of the Commandments makes an important point about the role of truth in communication. When the animals realize that the Commandments have changed, they blame themselves for having poor memories instead of blaming the pigs for changing the rules. Thus, the truth has become whatever the pigs claim it to be. The truth is now a propaganda tool, designed to reinforce the pig's domination on the farm.