I feel like the only things that would react to a character's alignment should be things that actually CAN see a character's alignment. For example a Sprite or Unicorn can know it and react accordingly and it is part of their more out there beings. A sprite can know an alignment by touching someone and would likely attack an "evil" character unless sufficiently dissuaded and would possibly help a "good" character.
Also I don't think we should see our Companion's Alignments at the beginning, but I do think it should be an invisible thing that exists. Only becoming clear if they say cast that cleric spell that literally has its effect based on Alignment or a Pact of the Chain Warlock touches them with a Sprite, and even then things can be ambiguous.
We could see that say Gale has an Evil or Neutral alignment, but that doesn't tell much about him in the moment, just how much he has done in the past. And perhaps we detect that alignment cause of the orb in his chest which is marked as evil and thus bleeds into him, even if he is squarely neutral or even good (though I don't feel he is, one could actually make an argument he is). Alignment can be weird and knowing it still doesn't reduce the character or tell much beyond what the universe has calculated them as. Someone seeking redemption can still be marked as evil, and someone ordering an atrocity can still be marked as good. Afterwards their alignments change, but in the moment the universe and magic sees them as such. Or uh thats how I see it.
