Recently I noticed a rather buggy example in the user contributed comment below the core API page for hook_menu_alter.
As a result, I raised an issue about buggy user provided documentation in the webmasters issue queue, that you can see here.
This received the following comment from core maintainer Jennifer Hodgdon:
But I'm not sure that we have a policy of removing comments with incorrect code in them.
Intrigued, I searched the webmasters sub-site, and I could not find such a policy.
However, more worrying, I could not find a policy document at all (I may have overlooked it, but I looked in all the obvious places).
If a site like Drupal.org is going to succeed as an authoritative source of information for Drupal developers and users, it need (at least) to have open, accessible and transparent policies about what is on-topic and what is not.
And as a site that seems to rely on user-contributed comments to explain how to use the code, it also need to have policies about curating content, including the removal of buggy code. Developers looking for information can not be expected to sift through long threads of comments to be able to separate the wheat from the chaff.
A policy document is also necessary in able to bring new webmasters up to speed.
As an outsider, it looks like Drupal.org webmasters is some sort of cabal that manages the site according to some secret rules passed from mouth to mouth. I do not think this is a model that scales very well, and that creating and maintaining a webmaster's policy document should be given priority.

Comments
For drupal.org itself...
I'd just like to point out that we do have a (very very short) "policy document" about comments on drupal.org documentation pages. In the right sidebar of pages such as http://drupal.org/node/1445720, in the paragraph about the copyright and licenses, you will see:
"Comments on documentation pages are used to improve content and then deleted."
And we have a page on how to do this:
http://drupal.org/node/135589
And... actually that jogged my memory. We do have this page that explains the policy about comments on both documentation and api.drupal.org:
http://drupal.org/node/14345
That page says that if you find an api.drupal.org comment with an error, you should file an issue, so that kind of implies we should remove the comment... I'll add this information to the issue.
Thanks for starting this discussion though! It may be useful to make a Webmasters guide if one does not already exist.
Drupal programmer - http://poplarware.com
Drupal author - http://shop.oreilly.com/product/0636920034612.do
Drupal contributor - https://www.drupal.org/u/jhodgdon
Hm... mistake
Actually the comment standards doc only says to file an issue if you find a problem in a documentation page. It doesn't say you should do so if you find an problem in a comment on api.drupal.org.
Drupal programmer - http://poplarware.com
Drupal author - http://shop.oreilly.com/product/0636920034612.do
Drupal contributor - https://www.drupal.org/u/jhodgdon
Creation of policies
Hopefully this is something the proposed working groups can get going on. As I've understood it, their purpose is to formalize a lot of stuff like this. http://drupal.org/node/1934018
Your comment about "some sort of cabal that manages the site according to some secret rules passed from mouth to mouth" has unfortunately been how outsiders feel about most of the "teams" surrounding Drupal.
Policy for curating API documentation comments needed
Many thanks to jhodgdon for providing links that cleared up a lot of things for me.
First, there seems to exist a policy document that at least tells you who can edit what, and some guidelines for doing that. Great! This document is Commenting on community documentation pages and API pages. I think the title should be changed into in line with its true scope (for instance "Curating community documentation pages and API pages") - but the content is good.
It makes it clear that a community documentation page is a wiki, that anyone can edit, and that rolling comments into the page and then flagging the comment rolled in for deletion is the accepted procedure. I think this type of crowdsourcing for producing and maintaining documentation is good. So I've got no gripes here: Just leave this the way it is.
The policy page also tells you how to fix errors in the API documentation itself (file an issue to get it corrected at the source). Fine, this is the way it has to be. This is not something one would want to crowdsource.
However, the page fails to mention how to curate the user comments that come as part of the API documentation. And I think I know why: Since the API documentation pages is not a wiki, curating comments can not easily be crowdsourced, and core maintainers are too busy with more important tasks, so they're not going to do this.
However, having well curated API support documentation is critical for Drupal to be successful.
I also think that adopting the model already in place for curating community documentation comments, for API documentation comments, is possible, with just minor tweaks to the setup:
Two (alternative) suggestions:
The above suggestions of course imply that we want the documentation provided in the form of comments on the API pages to be curated. I strongly believe that we want this. The fact that a lot of people are turning to Drupal Answers @ Stackexchange (which is designed specifically for the purpose of crowdsourcing curation of documentation) indicates that Drupal.org need to become better at crowdsourcing curation of documentation to remain on the horizon as a good source of information for developers looking for information about Drupal.