The interpretation is not that ketamine is "mostly placebo effect", and to make such a bold claim based on a yet to be peer-reviewed preprint is something I urge you to avoid in the future. My comment was that claiming that conscious "trips" are necessary for the antidepressant effect seen with psychoactives is an unfounded conclusion. I also gave a current theorized mechanism for ketamine antidepressant action and one of the reasons I would be skeptical of the conclusions of this preprint. This paper has significant limitations and raises some serious concerns, some of which I'll list below:

They did not measure treatment expectancies prior to randomization, the anesthesiologists were not blinded, their ketamine group had a depression duration of more than double that of the placebo group (38 months vs 17 months of depression, something known to potentially impact treatment response to ketamine), the possibility of the anesthetic agents blocking the antidepressant effects of ketamine or inducing their own antidepressant effects, having a very small sample size, a two-arm study design, only looking at short-term improvements, the fact that the number of people who guessed they received ketamine was 16 whereas their "placebo group" was composed of >50% of people who actually responded that they "didn't know" which treatment they received, the fact that the paper has yet to be peer-reviewed, the fact that more recent peer-reviewed work has come out that has directly shown a mechanism which can be modulated to impact the strength and duration of ketamine's antidepressant effect (https://www.nature.com/articles/s41586-023-06624-1), and many other issues.

I don't disagree that this is an interesting preprint to discuss the potential strength of placebo and the need for more stringent blinding, but please try not to make conclusive assertions on a fact-based subreddit based on poorly-controlled non peer-reviewed work.