Small mercies. We have been listened to, but only after a fashion.
The upshot of the blog update is that the Modern Comments concept is not disappearing (that was obviously never going to happen after reading some of the earlier info on it) and that the "Opt-out" will continue until such a time that Modern Comments works more like legacy comments (not necessarily wholly like them, though, it would seem).
I daresay we/I can give you feedback on the October outcome now:
Do I want "@" functionality? No, in 99.99% of situations it will never ever be required, and in my day job it is an absolute requirement not to be dealing directly with an author in near real time (they have a day job to do too and don't want being updated as I work through a document) or some intermediary who has entered comments into a doc. So I want a toggle to remove it's function, as I understand some will want its functionality.
Do I want to physically "Post" comments if not using @ functionality? An emphatic NO! Extra keystrokes equates to more work and more time spent doing something for the same financial return.
Do we want formatting capability in comments? Yes. Bold, italic, strikethrough, underline and colour are absolute minimum requirements. Spell check would be nice but is not a deal breaker (for me).
Direct MathType functionality is 100% required. Having to work in the Reviewing Pane is always a right royal pain at the best of times, when workflow dictates that every little document change is recorded. It can take on the order of minutes to arrive at where I want to be as the pane populates! That is NOT a solution to MathType (or image use) functionality in comments.
Will I be updating to the new "Opt-out" version? Not immediately. I will wait to see some more feedback here, as the current registry hack version works just how I want it to.