Could you maybe post your sun texture? It may be interesting to compare the visuals.

I edited part of glare.hlsl, (backup the file though) and replace these parts (file is in Modules\D3D9client folder):
I think I edited mostly rows with " // High frequency spikes "
// ====================================================================
// Creation of "glare" textures
// ====================================================================
// ======================================================================
// Render sun "Glare" (seen in space)
//
float4 CreateSunGlarePS(float u : TEXCOORD0, float v : TEXCOORD1) : COLOR
{
u = u * 2.0 - 1.0; v = v * 2.0 - 1.0;
float a = atan2(u, v);
float r = sqrt(u * u + v * v);
float q = 0.5f + 0.3f * pow(sin(3.0f * a), 4.0f);
float w = 0.5f + 0.2f * pow(sin(30.0f * a), 2.0f) * pow(sin(41.0f * a), 2.0f);
//float I = pow(max(0, 2.0f * (1 - r / q)), 12.0f);
//float K = pow(max(0, 2.0f * (1 - r / w)), 12.0f);
//float I = exp(max(0, 10.0f * (1 - r / q))) - 1.0f;
//float K = exp(max(0, 10.0f * (1 - r / w))) - 1.0f;
float L = pow(max(0, (1 - r / q)), 2.0f) * 3.0f; // Low frequency spikes
float H = pow(max(0, (1 - r / w)), 8.0f) * 5.0f; // High frequency spikes
float C = ilerp(0.03, 0.01, r) * 7.0f; // Core
float S = ilerp(1.7f, 0.35f, r); // Skirt
C *= C;
C += S * S * 0.40f;
return float4(max(L + C, H + C), 0, 0, 1);
}
// ======================================================================
// Render sun "Glare" (seen in atmosphere)
//
float4 CreateSunGlareAtmPS(float u : TEXCOORD0, float v : TEXCOORD1) : COLOR
{
u = u * 2.0 - 1.0; v = v * 2.0 - 1.0;
float a = atan2(u, v);
float r = sqrt(u * u + v * v);
float q = 0.5f + 1.0f * pow(sin(3.0f * a), 4.0f);
float w = 0.5f + 0.8f * pow(sin(10.0f * a), 2.0f) * pow(sin(6.0f * a), 2.0f);
float I = pow(max(0, (1 - r / q)), 3.0f) * 4;
float K = pow(max(0, (1 - r / w)), 8.0f) * 8;
float L = ilerp(0.05, 0.01, r) * 16.0f;
float T = max(0, max(I + L, K + L)) * 2.0f;
return float4(T, 0, 0, 1);
}