Privacy laws do not pertain to the same user using two different accounts
There are many privacy laws and they vary from country to country, and sometimes state to state. I don't know much about them. We have counsel to advise us on these matters, and what they say is final. I hope you understand.
if it was shill account, why wasn't that account closed
In shill bidding, all connected accounts are banned from the marketplace. That's been the policy for years. They don't get a second chance unlike transactions where the buyer or sellers decides they don't want to move forward with the deal, which we give a second chance to if no money or domains were taken.
I said our technology
and members. Members brought this to our attention and we've been working on it since then.
We catch the majority of shill bidding before any member gets involved. We also stop a significant amount of rule violations before they are ever possible. Of course, those never get talked about, only the ones that slip through the cracks.

No system is perfect but ours is as safe as it can possibly be given how an open marketplace works.
Which is comprised of who?
Directors, chief officers, etc. I am not going to name names so that members can attack them (Not talking about you, just in general), which I've personally experienced myself. Please stop asking. We deal with a lot of personal attacks for doing our jobs and we don't need to single team members out.
How long the ban period?
I have seen one member who was caught by namepros for the same shill bidding but now I can see him again active in buy & sell forum.
If you need name here you go
@Isac
It depends on the situation. If it's flagrant, then forever. With Isac, we never had 100% proof. We had signals/information and decided it was enough to give him a break from the marketplace while we further investigated. After a period of time without any new evidence, his story being plausible, etc., the restriction expires automatically. If it's a flagrant case of fraud and we are 100% positive of it, then the restriction never expires automatically.
A scammer is a scammer everywhere. So somebody can be restricted from the marketplace but they can participate in discussions here? Or am I reading that wrong? It's 1 forum.
We use restrictions to stop them from being able to scam members or violate the rules again. Similarly, a banned scammer on another marketplace can still comment on that company's blog posts (if their comments are open). They're separate services, but we make sure the necessary access is restricted. If we find that the restriction isn't enough, then we further restrict.
Restrictions can be taken all the way to exactly the same as a banned account. The degree of the restriction is shown to all moderators.