I’m sorry, but unfortunately, the idea in the comic can’t work.
Since spammers will also be the ones
rating those comments. And of course they will rate their own up. But even if not, they will be the vast majority.
So in the end, spam will be rated as highly constructive, and that’s the end of your little idea.

But 1. don’t be sad, cause 2. I already solved that problem.
The problem is, that you are making the same wrong assumption, that Wikipedia and every other forum on the net makes: You assume that there is one global view on the world. One global right and wrong. One global reality.
I’m sorry. There isn’t.
Even if the state of two human brains is
exactly the same, they at least still stand at different positions at the same time, or at the same position in different times. Which means that from a physical standpoint, reality is already relative. Now of course, as far as we know, physical rules are the same for both of them. But those rules already state, that even time is relative to your speed. But speed itself is only defined, relative to another object.
And all that doesn’t even matter much. Since human brains never are quite the same. What we call e.g. “helpful and constructive”, is entirely relative to our inner model of reality. It has to be compatible with that one, and it has to be information which makes it easier for us to survive, grow, etc. (= win natural selection). But with limited resources, one person’s winning is the other person’s losing. One person’s “helpful” is the other person’s “hurtful”. And really everything that does not fit in one’s own, very very personal, model of reality, is considered “not constructive”.
“Luckily”, most people are “cattle” for most topics. They blindly believe and follow the hive mind “reality”. Never questioning it. Never even thinking that you could question it. Never building their own sense of “right” and “wrong”. Which means their “right” is actually someone else’s “right”. And “right” just means “is useful to help
me win natural selection”. So they usually protect something that hurts them.
Now to answer the core question: What kind of system could make it impossible for spammers to disturb anyone? (Bonus question: And how can we kill off the forced “one true reality”?)
Well, nature already had a perfectly good system, before all those new forms of communication appeared. It’s called “network of trust”! You trust your friends and real leaders. They trust their friends and real leaders. And so on. Because you learned to know them and they knew you, and you worked in a team, because that made it much likelier for you to win in natural selection.
And nobody trusts a spammer. At least not after the first spamming. His bad reputation would always hurry ahead of him. Which means that nobody would want to spam others. Because he would have a very hard time finding anyone to even talk to after that.
Also in that network, reality is relative. There is no global “truth”. Truth is, what you and your trusted ones deem to be true. And that’s it.
You just have to implement this on the Internet. Which means, that the rating for each and every comment and in fact the whole view on reality, has to be by either you, someone you trust, or someone they trust, and so on. Just like for every element in HTML, every style information for it is defined, by cascading down from the most specific one to the least specific one.
So for forum spam, you could do three things:
2. Create comments with defined topics,
3. rate comments in specific topics, and
2. add/remove people you trust for specific topics.
And since those people would themselves have people they trust, and themselves add ratings on topics you trust them to be competent, down to the big leaders that create and aggregate a lot of ratings and that a lot of people trust, there would be a very personal view for everyone, without having to rate every single comment yourself. (In fact you could just leave all rating to others, if you trusted them.)
Yes that means you have to get to know other people, to be able to trust them. Sorry if you don’t like that, but that’s a core element of being human. If you start to lose natural selection (or in this case get lots of bullshit and spam to read), you will quickly appreciate its usefulness.

But imagine how a spammer could possibly infiltrate such a system. It would be impossible.
He would have to get lots and lots of people to trust him. And then send out the spam.
But that would mean that people would instantly remove him from their network of trust.
Also they would become a lot more wary about adding random people to their network. Which means that just creating a new user name and trying to get people to trust him again, would not only be a
lot of work again, but also be a lot harder, if not impossible.
And those who would blindly believe a hive mind that is also a source of spam, and not remove him… those would deserve what they get. They would be those who lose natural selection. And that would be a good thing. And they would not have the right to complain. Since they could just learn to distrust spammers. Or be more wary in general. Or find some real friends. Duh. If they can’t do that, then nobody’s gonna be sorry for them. Or maybe someone will sacrifice himself, to protect them… if he thinks they are valuable to him. Just like in RL.
I think it’s very nice and elegant. Which maybe is, because humans did it since the dawn of times, and it got perfected in all that time.