There is absolutely no doubt that we need rules. It is quite obvious that questions can easily get out-of-hand and go way beyond what is even remotely okay by all standards [and yet still be defined as legitimate questions by the current rules]. There is a definite need to draw the line and say "this is something that should be left to private discussion with your Rabbi."
On the other hand, any restriction we implement would result in certain topics of legitimate Jewish law and thought being off-limits.
Judaism.SE is a place where Jews go to learn about Judaism. Part of Judaism consists of the rules of modesty: i.e. there are something's we discuss in private and don't announce to the world. If we have a solid rule system in place that sets clear limits, there is no need to worry about this.
So what we have to do is decide on a set of rules (which may simply be "it's up to the moderators at the time" or "use your own judgement") and place them in the FAQ. Questions which violate those rules should be closed and deleted as off topic (which states "Questions on Jewish Life and Learning - Stack Exchange are expected to generally relate to judaism, within the scope defined in the faq.").
As you pointed out in the comment a key factor is about being explicit. I don't think the current question that brought this up is particularly explicit, but I do think that some of the answers that can come up may approach that problem. Which of course is a separate issue, but one that also has to be taken into account. It might be a good idea to comment every borderline questions "please respect the laws of Tznius when answering this question."