Same here, and I guess I'm a little famous here for my blood pressure experiments....N=1 experiments are still useful. I bought some MCT oil. Many say it gives you a burst of energy, improves athletic performance, blah blah. I thought it was worth a little try and: nothing. If there were even a small effect, I would have noticed. People put it in coffee, and I bet the only effect they are seeing is from the caffeine.
Actually, MCT oil was one of my n=1 successes.
Two years ago I had bulked up while making strength gains and wanted to get rid of some of the body fat while keeping muscle. That's difficult, because the body loves to hang on to fat and will even sacrifice muscle in order to protect the fat. I went very low carb and added in more LISS cardio. It worked to a point but then stalled. I tinkered around with different ideas, like adding in interval training to restart the process, but without success. MCT oil and grass fed butter in coffee restarted the process and in a few days I saw the fat melt away while hanging on to the muscle.
This January, I was coming off two years of strength gains with 23% BF. I spent five months working with a nutritionist and trainer to cut the fat. I got it to 20% and it stalled. The LISS cardio and very low carb diet got me to that point but then stalled for weeks, and then I started losing muscle. As soon as I started using MCT oil in my coffee again I began dropping 1/2% of body fat per week for the last 4 weeks, and I've gained all the lost muscle mass back and some more.
I think you made good points about the issues with n=1 experimentation - it's not going to work for everyone. And my method of self-experimentation is to science as a chainsaw is to a scalpel. That said, I've made tremendous improvements in my health without the use of prescription drugs.
It's all because I took one look at the path I was headed down and rejected what conventional medicine was offering. From that point on, it was all n=1 experimentation.
The majority of my n=1 success has been on better health via improving my nutrition, fitness and sleep, with supplements being used to support that, as opposed to supplements being the sole "fix" of anything.