So, I have to ask you something.
You say that we're "catering to professional appearance" and acting on "theoretical concerns about unprofessional-looking posts" without any "actual damage."
I don't think that's true. I think that jokes like this are actually harmful. I admit that I don't have the best evidence for this, but I have evidence. I've read ...
Here are some comments on your suggestions and the topic in general:
Professional mathematical interest in a question or an answer might well be a good necessary condition for MO but it will not make a good sufficient condition.
If the unprofessional content can be cleaned away easily, the posts can and should be edited.
If it cannot, then deletion is a ...