The last question was closed for being too broad (which is not, it asks how I can do a particular thing with MongoDB that just didn't got answered).
Maybe you have a marginal question there that can be improved. Questions are closed so that they can be either improved or deleted, not necessarily just deleted.
That question's title says:
Best way to intersect a big set with another big set from a database
And it was closed as "too broad."
Maybe you should edit the title to be more clear that you're specifically asking about 2 arrays in MongoDB. Using bullets to note your expected options might help as well.
You're likely not banned permanently, they just want you to fix your initial question, if you can. I'm sure if you fix it, you'll be able to ask more questions very soon.
When would be a good time for the site's administration to rethink?
While I don't intend to speak for Stackoverflow or the Programmer's community (I'm fairly new to Programmers) I believe we're trying to get to where we reopen more questions and get more questions answered without sacrificing quality.
So let's focus on getting your question improved so it can be reopened.