Blocks placed turn grass into dirt.

[MoBaT]

Any block placed such as a rail block will turn the grass into dirt. This is due to the lightreduction being a value of 15 on default for blocks and this code in the grassblock.cs in Craft.Net.Data

public override void OnScheduledUpdate(World world, Vector3 position)
{
var block = world.GetBlock(position + Vector3.Up);
if (block.LightReduction > 2)
world.SetBlock(position, new DirtBlock());
else
Grow(world, position, false);
base.OnScheduledUpdate(world, position);
}

Where (block.LightReduction > 2) is always going to be true for classes inheriting the block class.

At the moment I don't understand what's the point of having an integer for the light reduction code for blocks. I can see it being easier to just use a boolean. That's my understanding from looking at the code but you might have something in mind fore the future.

[ddevault]

Water, for example, has a light reduction value somewhere in the middle. I'll look into that, though.

[lancepioch]

In Minecraft each block is inherits a light value. This determines how much light the block "naturally gives off" or reflects. Certain blocks may reduce the light by more than one.