You might want to post this as a top level comment instead of a reply so it gets the attention it deserves.
I am somewhat afraid that such withdrawal would snuff out any further debate in the scientific community about proper ethical behavior and its delimitation ( which are admittedly fuzzy )
You have this exactly backward.
Far from "snuffing out" discussion of ethical behavior - the problem in the first place was that these researchers deliberately avoided the primary mechanism already in place to examine proper ethical behavior - their university's Institutional Review Board.
The withdrawal is not an attempt to silence the discussion regarding the ethics at stake. Quite to the contrary, the withdrawal itself is an explicit admission of ethical failings: "our study design was inappropriate: specifically, it involved conducting research on the Linux kernel community without obtaining appropriate consent and approval." They continue, further conceding the ethical debate "We are withdrawing the paper so that we do not benefit from an improperly conducted study ... [and] to prevent our misguided research method from being seen as a model for how to conduct studies in the future."
Nearly the entire issue at stake stems from the fact that these researchers did not properly use the Institutional Review Board already at their disposal. IRBs exist for the primary purpose of determining what proper ethical behavior IS, using existing widely-agreed-upon guidelines ("delimitation" in your terms) and judgment, and in ensuring such behaviors are followed. In particular, you normally must consult the IRB before any experiment is conducted on subjects. IRBs also serve as a primary party in the examination of any allegations of ethical misconduct.
The researchers in question only consulted their IRB after already conducting the research and publishing its abstract to twitter, for which they received "heated discussion and pushback," and were then forced to removed the abstract and apologize to their own IRB for causing "many confusions and misunderstandings" according to the linked article.