There are some custom weapons of Chaos Knight which were designed so that the default weapon particle effect still fits them.

These items have designated holes on the weapon where the particle effect is supposed to be. But the particle effect is missing on them. This goes for the following items:
1. Blade of Chaos Incarnate
2. Hellfire Edge

Furthermore, the following items, although not having a designated spot, are built so that the default particle effect still fits them well
1. Blade of Discord
2. Infernal Shredder
3. Waraxe of Lost Light

In this video, you can see how the particle fits all 5 items just fine. There is no need to disable it for them.