My assumption: Since “posters whose usernames began and ended with the same letter would have been safe”, and since “j” is technically the first and last letter of his username, I’m going to guess he’s have been safe.
J666 would have been safe for the reason Hal noted. Spatial Rift 47 would also have been safe because S is before T in the alphabet. Numbers weren’t counted in the rule.
I just feel bad for enipla and [c]nivlac**, who effectively made themselves targets. 