Please note: I'm not saying that's necessarily the case (that nakowa is cheating), but it's at least conceivable.
We should keep this possibility in mind. It would be great if doog could deliver more information about how the server seed is saved.
I think a short, but noticeably invest/divest delay would be helpful.
Here's how it could work: Divesting is always instantenous. Your initial invest is as well. But after any divest, another invest has to wait 1 hour. That's all.
This sounds like a reasonable idea. You'd also have to set a waiting period for withdrawal to avoid the creation of new accounts to reinvest immediately.