The conclusion of an earlier version of the essay read
If you take one thing away from this entire essay, remember this: as long as you feel good, sleeping anywhere between 5 and 8 hours a night seems basically fine for your health  (see Section 1), regardless of whatever Big Sleep wants you to believe.
All of the evidence we have about sleep and long-term health is in the form of those essentially meaningless correlational studies, but if you’re going to use bad science to guide your sleep habits, at least use accurate bad science.
 Assumption here being that “feeling good” is a valid indicator of how much sleep your organism requires.
The conclusion now reads
We have literally no idea about the optimal for long-term health sleep duration. 
All of the evidence we have about this is in the form of those essentially meaningless correlational studies, but if you’re going to use bad science to guide your sleep habits, at least use accurate bad science.
 Correction: originally, this sentence read, “as long as you feel good, sleeping anywhere between 5 and 8 hours a night seems basically fine for your health”, but as several people pointed out, ironically, the only support for this statement comes from the correlational data, which I claimed cannot be used to establish causality.
The alteration appears to be a retreat, but the new conclusion is a stronger and less defensible claim.
The original conclusion did not make a claim about sleep or causality. Saying something “seems basically fine” is a claim about one’s mental state. The charitable reader understands “seems” as “seems to me”, making this a self-documenting claim about the author’s point of view after 150+ hours of research. The conclusion states what the author concluded. The only way to discredit this statement is to question Guzey’s self-awareness, employing the Insanity Offense.
The “as long as you feel good” [i.e., not sleepy] disclaimer further reduces the scope of the claim. “Drink more water if you feel thirsty” is not a perfect rule, but it strikes a good balance between the risk of promoting anxiety among people who fail to drink exactly eight glasses a day and the risk of endorsing rare but genuine disorders.
Correlations are not meaningless. When people are eating more ice cream, the risk of murder is in fact higher. It is not completely unreasonable to worry about murder more when ice cream sales rise.
We surely have some idea about sleep duration and health. Drowsy driving is a realistic sleep-related health concern. Most people in good health probably sleep 5-8 hours and shouldn’t worry about sleep duration, despite Dr. Walker’s appeals. People sleeping less than four hours or more than nine hours should consider investigating the cause of their outlier sleep habits, which could help them identify health risks.
“Big Sleep” is funnier than “at least use accurate bad science.” The new phrase doesn’t make sense with the previous statement that bad correlational science gives us “no idea” about how sleep duration and health. What is the purpose of the red dashed line in the charts, if not to suggest that if you are getting 5-8 hours of sleep (and feel good), you probably don’t need to worry about your sleep duration?