I don't need this for a novel. I've just wondered if there were two people, say with a thick french accent, but who otherwise spoke English well, if their accent gets in the way or do they understand each other perfectly?
I had the same experience. My french is so-so, and I had much less of a problem understanding the french spoken by Greeks or Germans than I did the french spoken by native speakers.Back in my hitchiking days, I travelled around Europe with this guy I'd met along the way from Portugal. He didn't speak English and i didn't speak Portugese.
However we both had the equivalent of high school French and pretty much the same 3000 word vocabulary. We got along fine in our awful French most likely since neither of us were using any slang, local venaculur and we'd been taught a Parisian accent. (Although since I was from Quebec I could throw in a bit of the Quebequois accent known as Jouel just to piss off the Parisians!)
However we both had an awful time understanding the French spoken by the locals.
I mean who can really understand the French. The eat snails and frogs! They love Gerry Louis movies!
If their english is fluent, shared accent is no accent. Accent is purely relative, we all have one.