> Unban him from the forum. Then he'll (maybe) stop.
This is a very, very bad idea -- it's on a par with negotiating with terrorists.
> Maintaining control over your life and online reputation is more important than keeping him banned.
You seem not to realize that, by giving in to blackmail, one surrenders control of one's life to the next person who wants to engage in harassment. Also, what's to stop the original perpetrator from gloating about his victory over you and resuming or escalating his unacceptable behavior?
So, basically give in to bullying? Let the bully back into the forum, to potentially harass other users, continue doing whatever he was doing that got him banned? What's the point of having admin/mod rights if you aren't going to use them to make the forum a better place for the users?
Banning is a governance issue for any community. If the community is large enough, there may be other senior (by time and participation) community members willing to act in a leadership role. Ask for their help in formalizing the ban process.
The governance group (ideally excluding you) can engage the currently banned person in a public process on the forum, where terms of engagement are defined by the community, not lawyers or countries or emotional individuals.
If the costs (time, money, risk) of maintaining a forum become too high, other admins have closed their forum. Presumably the aggrieved party simply wants to participate in the forum, not destroy it.
There should probably be an open discussion on the forum engaging members and other moderators where the banned user can see it. Let them discuss the ban as well as the subsequent harassment and honor their decision.
I am a former admin of a large forum. I let trolls and spammers wear me down over years and regret that I did not handle some things openly.
Never ever do this. It will simply let people know that if you press buttons 'x, y and z' simultaneously that the owner of this forum will roll over and you can then kiss that forum goodbye as a venue for any kind of productive conversation.
Better to completely ignore the guy. And to tell your bosses and family about it and to tell them to ignore it too. That's the least effort for the most return.
After centuries of thought, humanity has developed some concepts beyond dualistic black & white. Everyone is free to choose the terms of their own engagement, rather than handing that power to the first-mover.
> After centuries of thought, humanity has developed some concepts beyond dualistic black & white.
Not giving in to blackmail is not about black and white, it's about black and black. And from a logical perspective, you don't mean "dualistic", you mean "excluded-middle" or "false dilemma".
I don't have an opinion on the blackmail topic. But the blackmail was preceded by a governance decision and other communities can provide advice or useful precedent. Even when the blackmail issue with this one person is addressed, the governance issue will remain and can re-appear at any moment.
Since solving the governance issue will have to be done at some time in the future, it can be done now and offers some chance of de-escalation. The blackmail issue can still be addressed through other means, including legal. But de-escalation helps everyone, now.
Not with someone who has already engaged in illegal behavior, as in this case (if the perpetrator and the victim lived in the same country, the perpetrator could be arrested for harassment). The perpetrator has already proven his rejection of civilized behavior, so dealing with him on that basis becomes foolishly one-sided.
This is a very, very bad idea -- it's on a par with negotiating with terrorists.
> Maintaining control over your life and online reputation is more important than keeping him banned.
You seem not to realize that, by giving in to blackmail, one surrenders control of one's life to the next person who wants to engage in harassment. Also, what's to stop the original perpetrator from gloating about his victory over you and resuming or escalating his unacceptable behavior?
No, this is not an option.