I haven't been able to figure out what Nxt does. This isn't because of poor Nxt coding. It's because I don't have the time to look into it. If a Nxt guru is around, please comment.
I am not a Nxt guru but i reviewed the Nxt Code and i understand the Nxt forging algo.
Qora's forging Algo is definitely better, if it actually works (safe).
I think the biggest secret is still hidden in these native files.
I am not a crypto-expert, but i think
the problem with ECDSA is that for a specific public key and specific data to sign there are several valid signatures. That makes it normally a bad choice to determinate the next forging account.
Qora must have somehow solved that problem.
But as long as these native libs are not OS we will not know how.