Welcome to CruiseMate Rivilian!
I just want to say how much I enjoy hearing the input and stories of people such as yourself. One of the reasons I love cruising so much is that it gives me the opportunity to experience different cultures.
Call me strange, but I found your story about the Vienna cafes fascinating (I know that is odd, but I really mean it). It just goes to show that what we consider "common courtesy," because we grew up with it, is not necessarily common in other cultures.
I recall being on a bus in a Greek Isle where there was very limited seating. The lady I was traveling with asked a young man if he minded if she sat on the tiny cushion over the engine block that was right behind the drivers seat. He replied with something like, "It would be my honor," in a thick British accent. It sounded so classy and courteous, especially from a younger man.
So I started using the same approach when people ask me if they can sit with me "Yes, please do, I would love some company". I noticed that after I got married this one little thing must have impressed my wife (who was not as well traveled) because even though I never said anything, she started doing the same thing when people asked her.
Rivilian, just so you know, not too many years ago it was common for every cruiser to be assigned a dining table with people they did not know and you would dine with them every night of the cruise. It was considered a big part of the cruising experience.
Today, with open seating, you will be asked "would you like a table for yourself or would you like to share a table?" If you say "share a table" you will be seated with others. So, it is still common to dine with "strangers" on cruise ships and I am sure most people find that to be one of the more interesting aspects of cruising. Most ships still offer the pre-assigned tables, but open seating is now actually more popular than traditional dining. On my last Princess cruise, for example, out of five (!) dining rooms only one was pre-assigned seating all night, and one other was from 6:00 to 8:00 pm. Three and a half dining rooms were open seating every night. That is a big change.
Most cruise ships still do "Vienna-style" seating for breakfast and lunch in the dining rooms - filling up table after table with everyone who comes in. I admit, this is a bit awkward and many people eat in silence. When you have one table with 10 people (five couples) it is a little difficult to start conversations. But I usually try.