Greg, there you go .. making generalizations ...
To address your points individually ..
1) My place of employment does not fold plans .. it does not mean that I have no experience in the matter .. it means that I have had experience, and my experience has taught me that it is very frequently not acceptable to fold plans .. so since every building department I have ever worked with will accept rolled plans, it became a policy to never fold them.
2) Perhaps there IS a reason to fold plans but I don't know of any that I think are good, besides making the plans difficult to use in the field, they come across as unprofessional .. I have had building departments and constactors refuse plans that were folded .. I might add that your city planning department is crazy ... I have a set of plans that comprise nearly 200 pages of documents .. heck we can't even roll them .. much less fold them .. I suppose your city planning department would refuse them because they are not folded ..
3) Never did .. I stated that we do not fold them .. I never even implied that it is not right for all situations. Once again .. the question was "How do you fold ..." I stated in what I thought was perfectly clear ... I(we) don't fold them ... I just didn't provide the reason.
4) Perhaps ... but he could have just been curious .. such as what kind of plotter or computer you use ..