I think the post you’re responding to is referring to well established results such as that there is no metabolic pathway to convert dietary protein to adipose tissue. While some dietary protein is glycolysized, that pathway only satisfies immediate energy needs. Excess dietary protein that isn’t used on lean tissue is eliminated by the kidneys.

Thats interesting.. so does that mean eating a lot of protein cannot make you gain fat? It would just be a tax on your kidneys instead?

Well in practice it would be very tough to over eat on protein alone. Assuming a 2000 calorie diet you'd need to eat over 500g of protein which is roughly 4lbs of chicken breast or 5lbs of tuna.

But at that point it would also be quite harmful to the kidneys

Unless you’re Dwayne Johnson.

Seriously though if you don’t have kidney disease then you really don’t have to worry about protein consumption.

Eating 5000 calories of veggies is impossible. That's like 25kg of tomatoes or 35kg of lettuce. You can't eat that in a day.

I think it may be difficult to eat that much just eating vegetables.