A couple of thoughts about this:
This whole “flooding with bullshit” was a technique I started deploying in 2008 to make myself harder to track online. And your idea of the “truth score” is REALLY open for subversion.
In the whole “flooding with bullshit” thing you mentioned made it harder to actually find the truth — as truth starts to follow a similar level of commonality as Sturgeon’s Law applies to things that are not terrible. This is what I started doing in 2008 after people started talking about how “be careful what you post online” and I figured out that was wrong.
So, to cover my ass, rather than limiting what I posted about myself — I posted more about myself. And found the ability to track stuff regarding me became much harder. People would focus on some really random stuff — and the more stuff there was to focus onto — the less likely they would focus on something that was important.
Essentially, it resulted in people stalking me to start bikeshedding with the information about myself I was giving. Hell, data mining algorithms still have issues not bikeshedding my info I not only freely give: but I flood the internet with.
The other issue has already been covered by various Science fiction writers, episodes of the Twilight Zone and stuff along those lines, for how a “truthfulness score” would end up being able to be subverted.
A computer algorithm would be ridiculously easy to be fooled in that area — as AI barely has the intellectual capacity of a toddler at these point in time.
Hell, even websites like Wikipedia have issues with ensuring staff members actually know what they are on about.
We’d literally need to start hiring experts in various fields to constantly review stuff being posted on the internet. Imagine being a teacher for middle school… but everyday for the entire internet. What is more — a lot of middle school teachers get things they are trained about wrong — which leads to further issues.
This is without the sort of people who stalk and harass people online coming up with ways to subvert the system as a form of internet social gaslighting.
I mean — we have issues with YouTube copyright trolling being handled — and that system would require a sufficently less amount of manpower to actually fix it.
Essentially… what you are talking about is standard science fiction day dreaming — and you can find publications from the 1960s and 1970s saying this is something that can be done… and then various failed attempts. Perhaps look into those?