++ bum-man
I hope so, that would end these types of threads for all time. Whoever is here wanting some closure or for people to accept their viewpoint, best go somewhere else already.
That said, I'd like to second bum-man's comments - dictionaries get their meanings by cataloguing what people come to use a word for over time. It's not that their definition is the only acceptable usage and everyone must follow them. For example, the word 'cool' really means something that is lowish in temperature, or someone who is calm or unenthused. However, no dictionary these days would be complete if it didn't say that 'cool' can mean something that is fashionable, good looking, attractive or whatever - such as, "that t-shirt is cool!". This wasn't always the case, but perhaps from the 60s onwards. Dictionaries change with the times, so don't take their word as final - people are the arbiters and agents of language change and use, not dictionaries.
That said, I would have no problems calling the CLS either a sedan, but I can see where they're coming from with the 4-door-coupe thing. I'd humour them and call it that; but since the poll doesn't have that as an option, I decline to vote. It's a coupe of sorts, but definitely not like a 911.