Responses
Just replying to myself now that I mtl'd the special episodes (I skipped them before, my bad). The sharing of pain logic has been clarified by the authors/artists way back March 15 in the raws and they said that it is "sharing of pain and suffering (including wounds)", not "sharing of all sensations (including pleasure)" so yeah thanks for coming to my ted talk :)
so while they were doing it in ch 24 we will see dokkaebi biting minchan's nape and leaving a bitemark similar to a mating mark in an omegaverse setting (if you know what I mean), but then it faintly fades right away in the next panel (reducing into a bruise), and it is shown that on that same area in dokkaebi's nape, there's clearly no trace of bitemark (even a faint one, as in none). which means the wound that dokkaebi just did to minchan through that bite did not reflect to his own body.
I think the pain while doing it in the midst of pleasure is not shared. Sorry to burst your bubble about dokkaebi feeling it in his own hole while poking at the same time.
╮(￣▽￣)╭