DO: We've experimented with more explicit rules in the past. What happened was that members started seeing the forum as a game, trying to skirt as close to the edge of the rules - posting against the spirit of the forum rules, but not the letter. This results in a more unpleasant forum environment, and a higher load on the moderators. That's not an improved situation in either direction.
The point of this forum is to support a community around Diplomacy. This includes many common off-topic interests (eg games with deception/limited information, politics, etc), and discussion of Diplomacy the game.
We've been very clear that we want to keep the forum welcoming, because it's on the front page of the site, and we have nearly 3,000 active users every month. For this reason, we have rules about being civil to each other, and work to reduce straight up trolling/abuse.
Removing the forum from the front page has been discussed in the past (which would neatly sidestep the "the forum represents the site" argument), but this idea has always been unpopular; many forum regulars say that having the forum on the front page is what drew them in in the first place. I think that's a fair argument.
I have some draft code for integrating a more featured forum (including Diplomacy, Forum Games and an Off-Topic board), which would reduce the impact of spam threads- and it would be possible for members to configure which boards appear on their home page. However, while we have the single threaded forum that we currently have, it's necessary to curb the number of spam threads.
I'm sorry that you feel that the forum is low key and dead- but this view isn't shared by everyone. Those who enjoy the forum do regularly complain about spam - often we don't do anything about it when it's just an extra thread, or when only one user has complained. However, when several users complain, and when the site rules are clearly being broken, we step in.
I'd like to note that BB apologised privately - which wasn't necessary, but was (and is always) appreciated.
A large part of Zultar's focus as site co-owner has been to reduce toxic forum behaviour - we don't want to end up like the community on (for example) EpicMafia - that's not what we want for the future of this site. I think that his effort has been very successful - people are generally more civil to each other, and yet discussion continues.
Now, sure, forum spam isn't the same as trolling/abuse - but it does contribute to making the forum harder to use. Consequently, no one was silenced or banned, and I don't expect that to happen here. And, as Riot has pointed out - flooding the forums has been against our site rules for a very long time.
This is open and shut - BB said he didn't think it was against the site rules, and when we pointed out that it was, he apologised. It's really very simple.
"People will +1 whatever the mods say."
This has ....not been my experience :)