Fanny You asked me a question on what seems to be a now deleted thread - brought my answer here as I feel it might shed a bit of light.
Fanny I can't answer for GN, but my own experience of moderating similar types of discussion sites would say that yes, they pretty much rely on reporting. Moderating is usually just a side role in what in essence a business that uses a forum/community etc to drive traffic towards advertising/non personal data collection etc. The money made by mining keywords and metadata is not insignificant these days so the main focus of anyone working for GN is likely to be in that area, not in monitoring what people are chatting about and will only intervene if their attention is drawn to it. They make it clear in their terms.
I can't state this as fact but my reasonably educated guess would be for GN itself - it's not a single entity, it's a 'product' of part of a much bigger concern - I doubt it has its own set of staff - when you see 'NellGransnet" on a an email - the suffix is so that NellMumsnet, or NellLeaf, or whatever, knows which bit of the business they need to look at. It doesn't necessarily mean they have a single role within a fairly large organisation. Which is also likely why the PM's haven't been fixed - allowing older ladies/gents to chat over PM is just not likely to be a priority in a larger business. It will no doubt get sorted, but not in too much of a hurry.
Places like GN are not a public service, they're businesses and on the internet their asset is information 'you' provide, not you as an individual. Harsh, but often true. The only way it would be different is if we had to pay a subscription to join and that was the main source of income. Even then, it wouldn't vary much.