error X3000: Illegal character in shader file

I pasted a line of shader code from SO and now my project refuses to work.

• I removed the tainted line of code.

• I've re-written the shader multiple times from scratch using VS, Notepad and Notepad++ as suggested on the Unity forums.

• I've used the hex editor view in Notepad++ to rule out the first two bytes aren't 0xFE 0xFF as suggested on this gamedev question.

I really can't figure this one out. I'm grateful for any suggestions you might have.

cbuffer CB_PER_FRAME : register(b0)
{
    column_major float4x4 view;
    column_major float4x4 proj;
    float4 eyePosition;
};

struct VertexInput
{
    float3 position : POSITION;
    float3 normal   : NORMAL;
    float2 texCoord : TEXCOORD;

    row_major float4x4 world : WORLD;
    float4 color : COLOR;
    uint instanceID : SV_InstanceID;
};

struct PixelInput
{
    float4 position : SV_POSITION;
    float3 normal   : NORMAL;
    float2 texCoord : TEXCOORD;
    float4 color    : COLOR;
};

PixelInput VertexShaderMain( VertexInput vertexInput )
{
    PixelInput pixelInput (PixelInput)0;

    pixelInput.position = mul( float4( pixelInput.position, 1.0f ), vertexInput.world );
    pixelInput.position = mul( pixelInput.position, view );
    pixelInput.position = mul( pixelInput.position, proj );

    pixelInput.normal = normalize( mul( pixelInput.normal, (float3x3)vertexInput.world ) );
    pixelInput.texCoord = vertexInput.color;
    pixelInput.color = vertexInput.color;

    return pixelInput;
}

float4 PixelShaderMain( PixelInput pixelInput ) : SV_Target
{
    return pixelInput.color;
}