First of all let me thank you for taking your time to write this in depth explanation It is clear to me now after your explanation and that of others in the noticeboard that as the US Copyright Office indicates there is no mathematical rule for the amount of material one quotes Also as pointed out by you and the copyright office it is not very clear as what counts for a violation and what not in the first look and the matter is judgmental in nature Therefore one would be better safe than sorry to just avoid direct quotes as much as possible Stay out of trouble as they say