Simple answer: the 19 witnesses have been vetted over a span of time as 'rational, benevolent actors' to the ecosystem.
The behavior of the entity wanting to mine is using an exploit apparently and would likely not be 'benevolent'. The 19 witnesses are keeping it out.
So how come this doesn't effect the mining power of the 19 benevolent actors? Do they have some sort of advantage over everyone else also? And without a hard fork, would the supercomputer eventually end up on the list of 19? I do not understand the process with Steemit, but from my limited understanding it sounds like there is some degree of centralisation going on?
Thanks for your reply. So does that mean that the mining is going on without interruptions? Only that these non-benevolent miners are ignored?
It just means he has a huge advantage over miners who arent using an exploit, so he gets most of the rewards. The total amount of mining rewards is unaffected and even if the miner is malicious (which we don't know) there isn't really anything he can do to harm the system. He just gets a bit of extra rewards, but even that isn't a huge amount. It is equivalent to what one of the top 19 witnesses gets, and when it comes down to it, he's doing the same thing (signing blocks).
Thank you for this quick explanation.