The letter was signed by the The NumFOCUS Code of Conduct Enforcement Committee. The members of that committee are listed on their code of conduct site. Seems pretty transparent to me.
They caused a lot of grief to a particular person. It is only appropriate to sign their apology with their own names rather than a "committee", don't you think?
That was the committee at the time of writing. If anyone refers to this in, say, a year, they will have no idea who was responsible. As an analogy, transaction histories, if done in a DB, are not normalized because you wouldn't want the price and total sale of a past transaction to change when you later change the price of the items that were in that transaction. Sometimes, it's actually good to duplicate code/data/effort, especially if it helps to make something clear.
Sounds like The Code of Conduct Enforcement Team themselves need a code of conduct to operate against.
I recommend immediately establishing a Code of Conduct Enforcement Team Code of Conduct. And since any CoC is meaningless when not enforced, there needs to be a Code of Conduct Enforcement Team Code of Conduct Enforcement Team.
https://numfocus.org/code-of-conduct#persons-responsible