[no spam] ramifications_of_tweaks_to_subject_line :) - Was: ramifications of tweaks to subject line

[Sebastian Schwarz]

On 2017-01-12, RW via freebsd-questions wrote:
> There's a rather complicated document out there somewhere that
> details how to do robust threading that takes account of this,
> and it does include the subject.  Whether any clients are
> still using this algorithm I don't know.

You might be thinking of https://www.jwz.org/doc/threading.html.
mu implements that:
https://github.com/djcb/mu/blob/67f74d44b0f525e6e588baf08c62cdaf668399fd/lib/mu-threader.c#L27