Great post!

I’ve managed a couple of small communities of my own, and was a volunteer moderator at a top-tier game studio for over 10 years.

The additional rules I’d add in are:

1. Be careful who you invite to be the first few to join the forum. They will set the tone for the rest of it — in other words, invite the kindest, most fun people to join before you open it up to the public.
2. Be careful who you invite to moderate (administrate, manage the community, etc.). The major studio who invited me to help them had an unwritten rule that anyone who wanted to moderate was immediately disqualified from doing so. Your ideal moderator is not someone who wants to wield power, but someone who is willing to take out the trash for the sake of the community (that they know they’re immediately no longer a part of the minute they agree to do it).
3. Be constantly active in your community. As your studio grows, it can be harder and harder to have a close relationship with your members and moderators, and that can get tricky when the member-count runs into the millions. Without that close relationship, it’s almost impossible to maintain the spirit of the community.
4. The point about acceptable humour is spot-on — but that acceptability changes when your community grows. When it’s in the hundreds or even thousands, everyone knows each other — so you can make a joke like “waiter! Fetch me the banhammer!” and everyone will laugh. When you’re in the millions, at least one person will be offended (even if nobody was banned!) and even if apologies are issued privately, you don’t have the kind of community where people will assume goodwill (because people don’t know each other), so it creates problems — they think the moderators are heavy-handed — and the only solution (effectively) is to ban humour. That’s overstating it, but will be familiar to anyone running a corporate community or social media page.