I wonder if you (Scandinavians or non-Scandinavians) have ever been in a situation where you didn't understand one word (that's what the title means, roughly) when you heard other people speaking (a dialect of) your own language. Norwegian is supposed to be difficult because of all the dialects, but I've never been in a situation where I couldn't understand a word of what people were saying, or anything approaching that. Whereas with English, I find it really difficult to understand two people with a thick Glasgow accent talking together and in Belfast once, there were two people sitting in front of me on the bus talking for about five minutes, and I honestly didn't understand one word! (and they weren't speaking Irish!). I would guess that there are some Danish dialects that are hard (impossible?) to understand for a Dane who's never lived in that area, probably less so with Swedish and Norwegian.