I'm not familiar at all with the moderating part, reviewing question tool, so maybe this is irrelevant.
I just wondered if it is really necessary to write 4 comments all explaining the same thing to the author of an unclear question : an example
No, it's not necessary. Thanks for escalating this to meta.
One good comment would have been sufficient. The issue with that comments in that specific thread is that any later comment added another snippet of information for the author. My last comment was the most complete one.
As a moderator I always feel a little bit guilty after closing questions. And since my name is directly linked to the closing of the question, I always feel obligated to leave a comment providing the best guidance possible to educate the community and the poster about how to improve the question.
As you may have noticed, the important part of my comment is a link to the help center of the Ethereum Stack Exchange site.
Related to the linked question are, probably:
I would always encourage users to not only post a comment which requests improvement of the post but also -- if possible -- link related help center articles to educate the authors and the bypassing community about what could be improved.
PS. Also have a look at Frequently Used Comments and feel free to contribute.
Splice Struct Entry by Index in Solidity was a good example of a question that should be flagged->"should be closed"->"unclear what your asking".
I suspect early commenters were not familiar with that feature, and if it had been done, moderator intervention would probably have happened earlier.
As an aside: the "should be closed" part is/sounds a little inaccurate, since it's actually just putting the question "on hold". And the 2 step process, instead of a single "flag question since it's unclear what it's asking", probably also contributes to users not finding this feature.