Why is it a prisoner's dilemma?
- Nobody writes follow-ups: everyone has an equal chance of being noticed and only has to write one email (and the recipient gets relatively little mail).
- You write follow-ups, but nobody else does: you get an overproportional chance of being viewed at the expense of everyone writing just one mail. Also you have to put up more work to organise and write the follow-ups, but that is very much worth the extra benefit for you.
- You write one mail, and everybody writes follow-ups: you get an under-proportional chance of being found in the sea of mails, much to your dismay.
- Everybody writes follow-ups (what TFA suggests): everyone has equal chances of being noticed, but everyone has to put up the extra work for the follow-ups (and the recipient gets a factor of three more mails).
My personal opinion on the article is that it is greatly damaging, as it is difficult as hell for society to effectively normalize "cooperate" behavior in such situations, even without voices suggesting "defecting" is your moral responsibility.