Irrlicht Engine

Alright. I just solved, with the help of some other threads here, the infamous transparent material z-buffering problem as it existed in my project. However, I'm kinda curious-

Driver->setAllowZWriteOnTransparent(true);

apparently did nothing, while

Scenemanager->getParameters()->setAttribute(scene::ALLOW_ZWRITE_ON_TRANSPARENT,true);

worked like a charm. What do the two approaches do differently, and is there a need for both in the engine?

There's documentation coming with those methods. You're simply not supposed to call the driver method, it's an internal propagation method which is exposed instead of being handled by the friend mechanism.