Yes! I had trouble deciding whether I should consider cities like London, Hamburg etc. coastal for a quiz about the largest coastal cities in Europe. I decided to include them there, especially since they have some of the largest ports in Europe, meaning that they are closely connected with the sea, so for the sake of consistency I excluded London here with a caveat about cities on river estuaries and cities whose urban area reaches the coast.
The reason I chose to include Glasgow is that the urban area seemingly ends right before the Clyde empties into the sea, at least from what one can tell by looking at the width of the river and Google Earth's delineation of the coastline. This isn't quite the case with London, where Gravesend, for example, can well be considered 'coastal'. Of course, the limits of the estuaries of rivers like the Clyde or the Thames are somewhat vague, so I'd be happy to hear more opinions on this.
Cities on large islands that don't touch the island's coast was indeed the idea, but you're right, Montreal technically fits the description I eventually gave. One problem, however, is that parts of the Montreal metro area are on the mainland, which clashes with the notion of the entire metro area fitting the parameters, which the quiz generally follows. Montreal would also have to be distinguished from other cities containing river islands, such as Paris or Berlin, and again, some argument about the city proper or a majority of the population would have to be made. Long story short, while Montreal is certainly an interesting potential answer, I think it would unfortunately be simpler in terms of the rules and the idea behind the quiz to leave it out. I've changed the description slightly (from "sea coast" to "island's coast") to reflect that.