Luhmann argued that moral communication loses influence in a functionally differentiated society because the function system are amoral. Moral communication cannot compete with the communication media of the economy and politics–i.e., money and power. But in a number of interesting publications, Vladislav Valentinov has argued that there has been a modern proliferation of moral communication. We might test this claim with the Google Ngram Viewer.
In English, the most common words in moral communication are probably good and bad. Here is an ngram for good+bad from 1800-2008:
There is a decline between 1900-1982, but then the trend line rises almost to where it was in 1800. Based on this data, the level of moral communication—i.e., communication centered on the distinction between good and bad–has not changed significantly since 1800. But, of course, a lot more research would be necessary to make a strong argument for or against the relative stability of moral communication.