I think the rule summarized in the title of this creative contribution would be necessary to follow in order not to turn the repository into just a record of people's personal content preferences. If this rule was not followed, in addition to simply their personal preferences the users would start posting/suggesting what they think generally matches well with psychedelic experience or what content/activities are psychedelic in their essence.
You might have certain inclinations while you are sober, but be drawn towards different things while being high, it's almost like the drug (or the state of consciousness caused by it) would choose for you, if you may. So I think having a certain statistically averaged pool of activities/things/content pieces that people liked exactly WHILE being under the influence of psychedelics would be a wise option vs having a mix of that and recommendations based on simply personal (sober) inclinations and knowledge of what is classified as psychedelic and therefore guiding others towards that.
If "the product" of such an online repository would represent the inclinations caused/ influenced by actual psychedelic experiences it would be a more objective representation of what type of activities/things/content does the psychedelic experience make people lean towards.
Of course, there's no way to ensure that people won't behave differently irrespectively of this rule, but the website could specifically and clearly emphasize it and ask politely for this while explaining why it is important, that would help decrease the number of suggestions that are not in line with the rule. Additionally, before you could recommend something, the site could ask you to fill in a section where you had to describe your experience and the circumstances of how you got to like something, what were you taking, etc. The anonymity of the users who recommend stuff based on their drug experiences could be ensured, there are ways to do that online.