What level of discourse are we aiming for here? What does our audience expect and desire? What are we capable of providing?
It is important to note that the topic of this site is intentionally and irrevocably middlebrow, like it or not. Grammar discussion and usage advice is an inherently middlebrow activity. To elevate it to something highbrow would require transmuting the entire nature of what we do here into what linguists do—that is, to study the phenomenon of language in a scientific way. While I personally find linguistics fascinating (that's why I have a degree in it), I also know that the audience for linguistics discussions is orders of magnitude smaller than the audience for discussions of English language and usage.
We can prevent the middlebrow from becoming lowbrow by demanding a certain level of seriousness from question-askers, and we are already doing a fine job of that. Complaints that we have too many low-quality questions are unfounded and unsupported by non-anecdotal (read: substantive) evidence. Furthermore, it must be remembered that lowbrow topics like taboo words and slang can be and are valid topics for serious investigation and discussion. Linguists can and do write very serious papers and theses about these topics. We are not a community of linguists, and such a highbrow approach is not appropriate for this site and our community. Lowbrow topics can and should be discussed here in a decidedly middlebrow way. I will NOT tolerate attempts to force us to squelch all discussion of taboo words, slang, vulgar speech, and the lexicon of anger and hate. They are valid topics of linguistic investigation.
This may be a semantic distinction, but I balk at the word middlebrow. That suggests we cut off the bottom and the top. Not that you need a dictionary citation, but let me air my fears a bit here:
middlebrow |ˈmidlˈbrou| informal chiefly derogatory adjective (of art or literature or a system of thought) demanding or involving only a moderate degree of intellectual application, typically as a result of not deviating from convention : middlebrow fiction.
I would suggest that we are more than that. I would hope that we embrace all of English, from the lowest and most vulgar to the loftiest and most refined — and, yes, everything in between. I suspect that's probably the essence of the answer you yourself supplied, but I wanted to make it clear that I don't believe "middlebrow" should mean either anti-intellectual or crusadingly mundane.