Thank you Deadnought! I take usability (how well concepts come across as well as general readability, pick-up and play) seriously. We play-tested the game twice and incorporated general feedback as well. I am happy it worked out even though I packed it with concepts. I will also look to make your feedback more clear in the pamphlet after the jam.
Regarding your question about the pilgrims, then it is also something that unfortunately got cut. Damn tiny pamphlet word count! But the idea is that the bloodletting and spinal tap is quite invasive and would lead to bodily decay regardless. The reason why the priest do it is because of their religious beliefs being exacerbated by the fungal growth in their body from genetically modifying themselves with the bioluminescent fungus from the planet. The fungus craves decaying material to "feed on" (decompose) and uses the priests as a kind of religious Angler fish light to lure in devoted but gullible pilgrims.
Regarding your question of OSE, then Mothership is actually my (almost) first experience in playing role-playing games. It's at least what got me hooked. And I do lean more towards the narrative end of the role-playing spectrum, which may be why I favored some more "theatrical" parts in the module, like the rite of passage. When running it, it was fun to ask the players what their sun-name was and have them whisper it in my ear, then putting a gene-gun to their foreheads. "MY CHILD. DO YOU ACCEPT TO LET THE LIGHT SHINE UPON YOU AND THROUGH YOU?!"... fear save.