It wasn't sys chat that was the issue. It does I'd the individuals causing the issue together with out of context 'reasons'.
In Morbads terms 'an explicit admission '.
Think 'bank robber posts pics'.
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Sorry I'm not really sure what your point is here. Any player certainly can state what their intentions are, its something I regularly do. That doesn't mean most do, nor that you should necessarily take them at their word. You can never be sure. The images you posted do not at face value show a criminal, they only show someone with bling.
At the most basic level, mode choice doesn't directly affect the experience of another player. Nobody in Open can instance with you, you can't instance with them. Not ideal but not unreasonable.
System chat crosses modes but can be disabled but doing so doesn't affect anyone but yourself. There is no downside to this to anyone but yourself.
Blocking other players while remaining in Open has the potential to disrupt instancing for other players. Morbad's point (AFAIK) is that it would be better for his game experience if he could instance with anyone that was willing to instance with him. Not to remove choice from anyone else, but to have any kind of player instancing filter affect the player doing the filtering (as modes do) rather than being one that affects his Cmdr.
This isn't my own stance on blocking (I gave it in my first post in this thread) but it does make sense & based on how Morbad has described his playstyle here, is consistent & understandable. Disabling chat or to a lesser extent mode choice don't affect other players, Blocking ideally shouldn't either. If I were to block another Cmdr I should reasonably expect to be the one who is deprioritized from instancing with other Cmdrs. Perhaps it already works this way, I have never tested it.