Actually the big thing is that Jim himself wants this to be a pleasant venue. Relaxed and friendly, where misfits can feel comfortable and mellow and nobody has to fumble for their blood pressure pills. The Be Nice Rule starts not with Iago, but with The Man Himself.
A topic can be locked a few ways. Some forums, like the Bar, have an automatic 7 day expiration at which point the thread locks. There were epic long threads gumming up the machinery, and when a personality conflict arose therin, it would often fester out into the rest of the forum. So if a thread gets so angry and ornery that it's pretty much become so bitter and toxic that it's not worth cleaning up and returning to the original topic, it'll be put down.
Moderators will lock a topic for violations of the prohibition on Touchy Topics like relgion, politics and the like.
Open up a thread about your favorite economic system, or your least favorite president, and boom! that thread's done. (Add stuff like that to someone else's thread, and you'll find your post getting editational snipping or deletion.) Couple of reasons for that. The fighting and ill will invariably spreads from the politics thread over to thingsup totally unrelated like a thread about Toot Toot and kittens. And the forum members utterly uninterested in politics find themselves getting spattered by the pissing contest. "I don't care about Republocratarianists! I just wanted to read about Mouse and say how neat I think what Harry did in Book XYZ!"
Another reason, and this is pure assumption on my part, is that Jim & Iago aren't interested in having their community become politicized in general, nor become associated with any political faction. Remember, this is my personal impression, not Word of Jim nor Writ of Iago.
Take the Baen Book's site, it is pretty much a Conservative Stronghold, for example. Got some liberal authors in the Baen stable, but the forums are Hard Right. So liberal fans understandably feel unwelcome there. As are moderates if they open their mouths on teh non-conservative side of things. I've also been to other book or media forums where the roles were reversed, political correctess ruled, and those with even moderate, center/right views on any topic were unwelcome. In those cases, people who wish to join that community are rejected because they do not hold the "proper" belief systems. (For example, on teh Baen forum I had a person literally follow me to every area I visited to find something to criticize, even to the "movies we can't do without" thread. Boy had to much time on his hands, took his hatin' too serious. All because on a thread in the political section, I invoked my 10 years in a Combat Plans experience to offer criticism of a warplan used by a politician he liked. That is a darn good reason to reject political topics for a foum like this one.
Preventing befaviour like that is why some topics are cut out by the roots.
Jim's got fans of all factions, and every gradient in between. So I have the impression that he wouldn't like to see one faction make the others feel unwelcome. Doesn't want one batch of his fans chasing away the others. He wants all his fans to be able to meet and enjoy and make friends without political affiliation becoming an issue, in an environment that's pleasant and relaxed. He wants his friends to get along.
Accorded Neutral Territory, just like this bar Jim writes about.
