In general Courts will have jurisdiction if either the victim or perpetrator of a crime is within their jurisdiction. In this case there are quite a few jurisdictions that meet this criteria including Texas, other US states, the UK and Australia.
I think you mean obiter dictum comments relating to Bitcoin. As far as I know there are no Courts in orbit yet :-)
Yes, obiter, it was auto corrected. And the hacking of @community321?
@community321 was attempting to returning stolen property to its rightful owners so his his/her actions in pursuit of this are legitimate.
While the actions of @community321 were clearly not expected by the conspiracy of thieves that implemented HF23, it is quite possible that he/she had control of the keys legitimately and simply refused to comply with the illegal instructions to participate in a theft.
For example if he/she was an employee or contractor of Justin Sun or Steemit Inc and had the keys as part of his/her job, it was entirely proper to refuse an illegal instruction and instead attempt to return stolen property to its owners.