I know that this will bring more debate about this, but take this with a grain of salt as it is a rumor.
I've just got an email from one of my sources. Now this does not come direct from him himself and he cannot personally verify the truth of this spoiler except to say that this person does work on Lost. Now this person could well be spreading a foiler but I personally think there is an air of truth in this.
- The person in the Coffin is Michael
- He is responsible for only 6 getting off the Island
- He also gets off under an Alias but is not known as an O6
- This is why no-one went to the funeral. If it had been a member of the O6 there would have been a media frenzy
- This is why Kate did not want to visit the coffin
Source: Source via DarkUFO