Wow! This forum looks dead! Two months later and nobody pianist or sound programmer here? 
Well, I’m not a pianist but I hope the following helps you:
- Click on Edit > Zone > Sample Osc > Loop Tab
- Expand the Program Tree
- Select layers ‘Dampers’ and ‘Dampers Off’ alternately, what can you see? Perhaps this article also helps you:
Sustain pedal - Wikipedia
However, the most important question for me about piano sounds in Halion would be: Where are the string resonance parameters? I’ve played hard and soft pianos and they have dedicated effects or parameters for the string resonance (sometimes hidden algorithms). I cannot find them in Halion. I’m not sure if that’s the reason why piano sounds aren’t convincing me when I play several keys simultaneously 
Any idea?