I see it's one of those threads where your're only allowed a single viewpoint so I'll see myself out.
For those worried about necrotic brain - we'll you're not forced to consume the tadpoles so you don't. I fail to see the issue here, but who or what is supposed to reward you for that (that's covered with tadpoles)?
No seriously where should the "pure" mechanic (btw LOL) stem from? There should be ingame explanation for the "powers of purity" or whatever you want to call them...
It's like arguing you should look younger than people using botox IRL - basically it comes down to autonomy to do what you want with your body...
And yes it's a fair point tadpoled brain is probably unhealthy for an individual and yet if the whole world and everyone alive in it depends on the powers of said individual, I'd argue it's only responsible to use every possible aid including the tadpoles for greater good.
If we return to the very first opportunity to use the tadpole powers - it might be the only option available to you to rescue Shadowheart and for all you know you're leaving her to die otherwise, so what's the "good aligned" option here?