If a reader of the story was to have been present at the feast in Cana (and if the two protagonists of the scene were speaking English), it is likely that said reader would have heard the head steward putting a tremendous amount of emphasis on the word “you” when he says to the bridegroom “You have kept the good wine until now!” Based on the presence of the honor competition in the honor and shame culture, and with the perceived intense slighting of the more honored guests perpetrated through the best wine now being served at the end of the feast to the less honored guests, this could certainly be seen as an attempt at self-preservation by the head steward.
Yes, what the head steward is doing is protecting himself and his own honor. He is not congratulating the bridegroom. Almost assuredly, these words to the bridegroom would have been spoken in a manner that would allow them to be heard, and heard well by the honored guests, so that as and when the new and better wine begins to be enjoyed by those who would normally have received the inferior wine (if any at all), the honored guests, who have now become the insulted guests, will see that the head steward recognized their honor status and hence the problems inherent in the situation.
The head steward, it would seem, wanted to position himself as being more concerned with the honor of these sure-to-be-offended guests than was the bridegroom, so that if and when the bridegroom relieved him of his duties as head steward, with this happening due to the public shaming that was now sure to be coming to the bridegroom because of the very words of the head steward and the service that was now taking place, he would be welcomed into the home of one of these other guests and charged with similar types of duties. Most importantly, his own honor would be undiminished.
Now it may seem as if the head steward is acting somewhat dishonorably here, but that would be over-reading the situation and ignoring a key feature provided by the text itself. It is clear that the head steward did not know the source of the new wine. The text is clear in its indication that he did not know, though the servants knew (John 2:9), while ironically also knowing that they were going to be the ones that got to drink the new wine, as regardless of the quality of the wine, the honored but insulted guests would not lower themselves to partake of the wine that was being provided to the servants and those at the tail end of the table service structure. What was transpiring was unthinkable. Indeed, it would strike the honored guests as absolutely impossible that the wine served to the less honorable and the servants would be better than what had been served to them.