Eric Stevens
Your definition of threading is not compulsory. Section 2.2.5 of RFC 1036 https://www.ietf.org/rfc/rfc1036.txt states:

" User interfaces need not make use of this header, but all automatically generated follow-ups should generate the "References" line for the benefit of systems that do use it, ..."

Note the use of the word 'should' as opposed the use of 'must'. It's not compulsory.

We have been over all this before. There is no point in going over it again.

Sandman
So why are you doing this all over again? You were proven wrong back then and I would have no problem proving you wrong again using the same facts. Why dig up arguments from the past like this?

Eric Stevens
Just to demonstrate the logicacl flaw in your claim that the only correct way to construct a thread is to rely on a feature, the use of which is optional.

Don't wind this argument up again or you will further irritate PeterN. Just accept that there is more than one way of looking at the matter.