There are different kinds of tips. Some which I think actually help YC if everyone knows them -- because YC wants to make the most accurate analysis possible i

There are different kinds of tips. Some which I think actually help YC if everyone knows them -- because YC wants to make the most accurate analysis possible in a short interview, it helps if everyone knows to give clear, direct, and succinct answers, be prepared to answer questions, don't depend on being able to show a demo, etc. The confidential information is more like Off The Record things during YC dinners, information about other companies, etc. There is much more information about other YC companies (especially batchmates), or speakers at YC dinners, which is confidential than there is information about YC itself which is confidential.