Very often questions posted using polemic and subjective terms are flagged as "primarily opinion based" and "unclear what you are asking" and closed.
Given the idiosyncratic and cryptic style of thinkers like Heidegger or Derrida, shouldn't Philosophy SE users be allowed to post questions phrased in a similar fashion? Is Philosophy SE inherently biased towards Analytic Philosophy styles just by the question guidelines and norms?
I think this is an interesting question after a sort. I would agree the SE tends to work better for analytic philosophy questions, especially logic. But I don't think that's "bias" or at least not in the negative sense. Logic questions are the most objectively answerable type of question.
Part of the answer with respect to SE and continental philosophy is a dual issue in the academic study of continental philosophy whereby the study of it is separate from the famous people way.
First, yes, some of the main figures (For example, Derrida, Levinas) in continental philosophy were terrible writers with interesting ideas. BUT, No, that doesn't mean it's acceptable to write in the way that they did. Thus, even for people writing in academic philosophy, just because some philosopher wrote in a certain way doesn't mean it's okay. In other words, that others write poetically, cryptically, poorly, or in French is not a license for us to do the same. IF anything, it's why we need to do it differently to give sensible answers to questions.
Second, we're not here to do philosophy; we are here to ask and answer questions related to philosophy (where philosophy is understood as the academic discipline generously defined). Most of the famous continentals who write that way cannot be bothered to explain anything. Instead, they just pound out tome after tome in an idiosyncratic vocabulary that their followers and readers must decipher (the last sentence may apply equally to many sub-disciplines in "analytic" philosophy). They themselves would not even be able to function in a SE-like environment.
On the other hand, we can only answer questions that are well-defined. I don't have any of your questions particularly in mind, but several askers give us questions that are poorly defined and "continental". As such, they are basically unanswerable. We get a lot of Nietzsche questions in this vein.
Third, the prototype SE is the regular stack overflow. People with programming questions and get answers. If the answer worked, upvote. If the answer doesn't downvote. Other SEs need to emulate to some extent the idea that the answers that work are the ones that explain the issue for the OP or those similarly situated. To make that work here, we need questions people understand and answers that clear things up.
Many issues in continental philosophy do not lend themselves well to this format. Moreover, many of them are often worded baldly as if one outcome is preferable without making that an explicit assumption. It reminds me of a question on the academia.SE where an advisor is dealing with a student who thinks he will be the next Einstein. Many people writing in continental philosophy and asking questions in it, think they are reaching profound insights so deep that few can comprehend them. It's not an attitude conducive to a functioning SE to work on that level.
If Kant wrote in German, why can't SE posts be in German?
Whilst this is perhaps taking your question ad absurdum, the point is: why would there be a meaningful relationship between philosophical texts and SE posts?
Well, for one thing part of the task of understanding difficult philosophical texts is to to understand how they use language; this means clarifying their references, their presuppositions, and what they are taking for granted and working against.
To do this whilst writing in continental style is probably not best practise.
