I agree, and that affects way more than signing requests. I think the forum is protected by CloudFare, but that is definitely not a complete solution to attacks.
The ideal solution would be to have something like a bitmessage mailing list, but that opens whole new problems to overcome, like who is authorized to send, what happens if that people is unavailable… And in case it is open, how stop that from becoming a spammy list.
Anyway I think that creating a “contingency plan” for Nu in case something goes wrong is yet a pending task.