The responsible vs. irresponsible disclosure question is "do you tell the responsible party ahead of time and give them time to repair it". From articles it certainly appears that ejmr learned how broken their code was prior to this paper being published.
But responsible vs irresponsible disclosure is not a question of "should this be disclosed at all?", which the security community as whole seems to have determined that the answer is "yes".
The problem is that ejmr was not anonymous, and if you publish something that is not anonymous, it is forever not anonymous.
The only option would be to not disclose that there was any problem, not notify people that their posts were not anonymous, and this paper (the actual "research" about where posters lived/worked?) could also not be published. Because any acknowledgement or indication that the you could get form id to ip in any forum would cause people to go "huh, how did they do that?" a Streisand effect your way to everyone knowing.
This is of course assuming that no one else interested in commenter identities has ever looked at ejmr either, because these researchers did not do anything clever to break the scheme.