It is important when people reply inline - which our membership is particularly fond of doing, particularly in email. I’ve replied to your post in a similar fashion to what our members want to be able to do reliably (I’ve used the web interface to do so - it works consistently here, they wish to do it by email).
Threading, as I mentioned, I believe is largely dealt with by mailing list mode, which I believe we’ve worked to make the default for all of our users.
I believe that getting quoting “fixed” will help us a lot in terms of member satisfaction (and potentially retention). It will also let those of us running the org to focus on other things. 