Soon to be a first-timer here (in about 3 weeks). What caught by attention was the discussion about sharing tables. When we lived for some years in Vienna, an early lesson on restaurant etiquette in general involved this practice.
Many restaurant venues are cramped, particularly in the older parts of a city (older, as in 1000 years old). Small cafes are crammed into the coziest places, and they are often packed. Consequently, there is no "waiting for a table" in the sense of waiting for a table all to yourself. Indeed, the waiter will seat a couple at a table where there are two empty chairs, even if it's already being used by another couple. Or with two single people who do not know one another.
The only exception to this was the type of restaurant that could cater to a large family or gang of diners. Those tables were set aside in another part of the restaurant and were never "invaded" by strangers.
At any rate, inviting folks to sit with you was expected. And, many times, you were given no choice, as the waiter made the choice for you!
In this respect, I think cruising will remind me of dining out in those years in Vienna.