I know that a good bit of the double posting is deliberate because of the way the subscriptions to threads work. An email is sent for each post, so some people just follow the thread via emails. But they can't see edits. That is why some people add another post instead of editing. Fix the board, and that problem is likely to go away.

Recommended reading - Netiquette http://www.albion.com/netiquette/introduction.html

As we all come from different cultures, this site has developed a culture. New people are welcome, but it is recommended that someone new do a bit of reading to get a feel for things before diving in. We don't have forum guidelines or FAQ yet, but that would be required reading I imagine. However, simply reading a few different threads in different forums gives a new person a feel for the existing culture and where they would like to start. This makes it easier for the new person and also for the veterans of the site. It's a lot easier to be welcoming when someone doesn't come barging in and trying to tell everyone what they should be doing. Asking questions is always a good thing, even if it's in the FAQ. I'd rather have someone ask than simply not know at all.

Anyway, the netiquette covers things from marking OT postings to handling spoilers to responding to trolls, etc.

That's it for me right now.

EDIT: Please forgive the rambly nature of the post. It's 4am, and I've been at the office since 11am yesterday. I'm a little silly, but hopefully I got my point out without sounding all controlling...

Cheers!
Em