I know this place loves very trigger happy moderation
Did you look past the title of that post, to the most upvoted answer, or did you just pick a title that would fit your narrative? Anyways, that answer does explain why this site is the way it is, and it's not because 'this place loves very trigger happy moderation'.
Should I copy the other post that stayed up, and just make up some stuff about how confronting whatever person is a good idea, and add in my experience at the start?
No, please do not copy answers. Duplicate answers are frowned upon, and are eligible for deletion.
Also, please refrain from 'just make up some stuff'. We can't check if everyone sharing their experiences is sharing genuine experiences, but since you've now admitted here you are willing to even consider the possibility, it's hard to take anything you will write going forward seriously.
Is interpersonal advise [sic] like "Talk to the person being blackmailed before you talk to the blackmailer, and seek out lawyers who are more experienced at interpersonal conflicts." forbidden?
Yes, 'advise' [sic] is forbidden. See this image, from the Good Subjective, Bad Subjective blog post. You're not here to 'give advise' [sic]. Every site on the SE network is supposed to be a repository of knowledge. Experience can be some form of knowledge, advice belongs in the same column as opinion and preference, in other words: It's bad subjective. That's why questions asking 'what should I do' are off-topic here. This site isn't here for advice. Again, the topvoted answer on that post you linked explains this very well.
You're supposed to stick with the premise of the question: OP wants to convince someone not to get revenge because that would humiliate their friend. To be fair, the question itself isn't the greatest either, it's asking us to throw ideas at a wall to see what sticks, instead of listing old/new arguments OP wants to present better. As our help/on-topic states we're not here to come up with new arguments for people, so the question is far from ideal.
As for 'seek a lawyer/professional': There's a reason IPS in the past had discussions about a site-specific close reason on needing professional help. So, if your answer is going to be 'you need a lawyer', it's not a matter of Interpersonal Skills anymore and should be closed as off-topic.
I posted this answer. which was deleted for not having interpersonal stuff. It did have interpersonal stuff, but part of the thrust was that when people intend to blackmail people, the professional negotiator and citation I cited says that it's not an easy thing to do to directly confront them, and it's better to have professionals do such things, because negotiating with blackmails is a complex skill that isn't quickly mastered.
So, the advice to 'get a professional' is something that shouldn't be in answers here, and that part is definitely not an 'interpersonal skill'. Your answer, the way it's written now, also seems to totally ignore the OP and their question (get better at convincing this 'enemy' not to take revenge), and instead focuses on suggesting things the rich closeted gay guy (and his girlfriend) should do, and then goes on to tell OP that only professionals can do what they want to do. Again, that last one isn't an Interpersonal Skill.
Your answer wasn't deleted for 'not having interpersonal stuff'. Back to that 'trigger happy moderation' post you linked, and the answer there that explains 'stuff' is not what this site is for. Your answer was deleted because none of the things above are interpersonal skills needed to solve the situation, as the link explains.