Maybe add any of the following features to avoid question duplication, like:
- Add to the question workflow a “Is this your question?” section/page, which does a search with terms of the new question
- Add to the question field an auto-complete for searching existing questions while the user type.
- Remove “Ask question” button, and make the search field an “Ask or create a new question”, which does a search, and if no results are found, proposes to add a new question.
I know the user should always do a search before adding a question, but I learned this the hard way by creating another duplicate of “What are the best window managers for Linux?”, which will be fixed as soon as “Topic deletion” is enabled.