1. Can different owners have Host mode On at the same time, what that does? Rough load balancing, random splitting of connections as OP observed, or none of those and just unacceptable state?
That post was a very early test when darkMX was just released.
There cannot be more than one simultaneous active host.
2. As was stated somewhere the owner doesn't have to be online as long as at least one of moderators or higher level users is online/connected....?
Tixati and fopnu work that way, not darkMX.
3. Also, from a physical security point of view, keeping a large file shares does not require to keep the network/channel private key on the machine. Normal user level on 'a server' will be sufficient thus desirable to protect the network/channel from hijacking by exporting a private key from such a cracked node. Is that right and preferred policy?
User share libraries and channel ownership/control are not related functions. A channel owner/host client might not have any shared files, or might have a million.
4. Related question: how to transfer hosting of network/channel to another owner so the ex-owner will lost the actual key/ownership and the key will be deleted/purged from ex's machine? Will that supposed to work ONLY by agreement that ex will set his Host OFF, then the new owner regenerates a new private key? Will the subscribed users remain preserved in such a transition?
As the notification says, use caution when sharing the root key because it is the key to the kingdom. But actually the users are in control. Anyone can create a root key and advertise it. But if no other user decides to join, then there is no channel. It takes at least 2 users to connect to make a channel. If an owner decides to share the root key with another, and they later have a falling out and can't cooperate, and both remain set as host, then the channel will split. But in that situation, the users have no control that I am aware of to select which owner they want to remain connected to. One owner will have to create a new root key, advertise it and the users will then decide if they want to connect to that owner's new channel. In effect, users are in control. They can't be forced to join any channel. It is only by user consent.