Could you please not post unsubstantive comments to Hacker News?
CO2 is a subset of pollution.
CO2 is not pollution. The concentration of CO2 on the atmosphere only has negative effects through warming (which is really bad). Plants actually enjoy increased CO2 concentration.
Now I am wondering, how much CO2 is too much for plants? And now when more CO2 is available, why don't see new forests appearing in places where there never were any forest.
Greenhouse operators often provide their plants with an atmosphere of 1200-1500 ppm CO2, which would fall into the
economically advantageous range. No idea where the "too much" range starts though.
Once we get to 1500 ppm the situation will be so bad that worrying about photosynthesis quality will be as unimportant as worrying about who wins the football cup.