As said somewhere else this does not prove anything. This could just happening as well if you fast. People fasting for a couple of weeks have reported better mental abilities as well. Nothing of what was written is unheard of, and besides you have to realize there is a placebo effect since the guy knows he is going to take Soylent and expects something out of it (even if he does not realize it himself). Placebo effect can be extremely powerful.
So this kind of first hand report has close to zero credibility.
So this kind of first hand report has close to zero credibility.