I don't have much experience with that community, but from the little I've seen, agreed. It's not good.
A good forum design will only get you so far, the rest is up to the moderators. If you let bad actors in, it doesn't matter how you designed your forum, they will poison the well and drive other people out.
The best communities I've been in are in independent old-style forums. One of them is Tildes. Most of these don't feature downvotes (or upvotes for that matter) and are honestly the better places to have discussions IMO.
I'm firmly against what Discord is doing (and what governments like UK, Australia - and soon others - as well).
The main reason is distrust. I do not trust that they - or anyone - would use this data responsibly and only for its intended purpose.
While I do not doubt that these measures could protect more children - I also do not doubt that these measures will be abused. Businesses will violate whatever privacy we still have left in order to get more money from info-brokers/ad-companies, and governments will use it for control. The US has been proving this with ICE, where they've been using Flock to target people.
That's why I always roll my eyes whenever these kind of measures are introduced. They're always introduced with "think of the children!" right beside them.
There's a reason why Apple - years ago - refused to develop a backdoor for iPhones when FBI requested/ordered them to do. There's just no proper way to prevent abuse with backdoors. Yesterday they wanted to check a criminal's phone, tomorrow they may want to target an annoying journalist.
Same principle with this tracking. Once Discord (or any others) can tell that your account belongs to you (IRL entity), there's nothing that you can do to prevent them from abusing that knowledge. Let's assume that today they use this new system for its intended purpose - who's to say that tomorrow they will?
Not mention the data breach discord suffered last year, where around 70k proof of age IDs were leaked. So not only you have to worry about Discord, you also have to worry about others that may get their hands on your info.
Don't get me wrong, we NEED to improve the safety of children on the internet. I fully support doing this via education, improving parental controls, maybe even banning children from social media apps until a certain age, etc.
But abusing our privacy rights is not it.