When a question is closed, its status is reflected in the title by appending
[closed]. However, users tend to occasionally post a questions like this one with square brackets in the title.
For one thing, isn't this what tags are for? Putting square brackets around a keyword in your title is just unnecessary. And more importantly, if square brackets were disallowed in titles, their presence would instantly alert people to a special condition within the system (like a question being
One way this could possibly be implemented would be to display a suggestion to use tags if a user tried to enter '
[' in the title of a question.