Before this thread starts to get filled by doomposting (please stop, I don't want Reddit 2), the plan is to keep both the new comments and the forums alive at the same time, with each having its own purpose.
Title and chapter comments on the new system, and general chatting and discussion here in the forums (so yeah, lurkers, you can keep lurking as you've been doing up until now).
You say this, but I'm not sure that what you've show really supports the idea that your intention is for both to be used. The per-chapter discussion forums are one of the main uses of the site's forums, so giving that role to a new system practically cripples them, doesn't it? If they really are phased out for "title and chapter comments," the only thing that's left will be the miscellaneous and off-topic discussions that the majority of users (especially new ones) won't especially care about.
Rather than "each having its own purpose," this seems more to me like the new system having its own purpose and the forums being left as strictly a backup for whenever the new comments aren't good enough. And in the first place, if the new system isn't good enough in these scenarios while the old system has already proven itself to be good enough in all these scenarios
plus the ones that the new system was explicitly designed for, what's the even the point of the new system?
I honestly can't think of any real justification for this change other than some misguided notion of "well, the big platforms like Twitter and Youtube use a system like this, so surely because they're successful it's a better system." But your userbase is already telling you that this system is worse.
The whole point of this "early access for supporters" thing is meant to be so that you can evaluate people's reactions, right? It's not just to incentivize people to give you money? I think that the reactions you've already gotten are more than enough to prove that this is a
change for the worse.
Anyways, I've seen how this goes on other platforms, so I know that you're probably just going to stick to it. But you could at least pretend to care what people think. You don't gotta be the next Google, making things worse for literally no reason other than because you feel like changing something.