I would guess that about 5 to 10% of people who seriously try the practise for an extended period experience very scary and potentially trauma inducing effects
So the lower bound of your estimate gives us ~200,000 people who would be adversely affected. Looking through negative reviews, it's all complaints about pricing and paywalls. The same is true for Headspace, the second biggest app in this space (I don't have DAUs for them, but it's got about half as many downloads and reviews, so let's assume less than half as big).
I can't find a single complaint about adverse mental health effects, which doesn't mean it never happens, but it's not anywhere close to 5%.
[1] https://blog.apptopia.com/calm-app-outperforms-headspace-dur...
The claimed hypothesis is absurd on its face. It's a wild and strong claim that needs strong evidence, so we don't need to be super precise here, if the effects were nearly as strong as 5-10%, we would see it.
We don't have to engage in crude methodology. We have tons of research.
Meditation research generally is low quality, as is suffers from lack of defined methodology, lack of a consensus definition of what meditation is, and the general subjective experience of meditation. (Concretely, if you want to do brain scans on someone meditating, how do you know they're actually meditating? This extends to scans on people who are "experienced practitioners", how do you know they are experienced practitioners?)
Regardless, the vast body of research does not point to negative effects, most point to mild positive effects, and the medical field considers it perfectly safe for healthy people. If you want to use research, don't pick and choose the studies that find adverse effects, look at the overall body of research.
It feels a lot like the goalposts are being moved here, the original claim was that meditation is extremely dangerous unless you're doing Buddhism right, now we're asking if there's evidence that it's completely safe.
I explicitly noted that there are probably rare cases where meditation leads to negative experiences (and I am not distinguishing between traditional methods and so-called secular methods, the risk should be the same for both, according to my model). But that is my point: these will be rare, and not extreme, except in people with pre-existing mental health issues. Normal, healthy people simply do not develop psychosis from meditation practice. Furthermore, there is no body of research or evidence known to me that shows that the (small in both effect size and frequency) risks are changed by the meditation practice or tradition. The research that we have shows small effects for meditation in any direction, but is overall positive regardless of tradition. My proposed experiment was an attempt at distinguishing between secular methods and traditional Buddhist methods, in an attempt to find any evidence of the massive effect size you claimed (5-10%!). This is the crux if the disagreement, not "can meditation EVER be dangerous in ANY circumstances", but "Under what circumstances, and how dangerous". I say, "Only in rare cases where there are underlying mental health issues regardless of tradition". You say, "Commonly (5-10%), for people who don't do Buddhism, and almost(?) never for those following Buddhist teachings". (I'm not actually sure if you think Buddhism removes all risk or is just much less risky, but either way I disagree.)
You made an outrageous claim that you've still provided no evidence for, and you've constructed a straw man of my argument to knock down. You're not arguing in good faith.
I'd be happy to reset if you want to discuss the relative difference in risks between Buddhist and secular methods (evidence on other meditation traditions would also be welcome), but I'm not going to argue with you about the words I've written and their plain meaning.
Again, this is a huge bold statement, on what basis are you making it? You are the one making outrageous claims, and constructing strawmen. If I am a bad discussion partner, you are a dire one.
There are plenty of apps out there with millions of daily active users. What percentage of those users do you expect to suffer negative mental health side effects? Where is the evidence that they exist at all?