Maybe you should add a throttle for new questions based on the average of votes of the user's past questions*.

For example, if the average scoring of questions asked in the last 30 days is -0.5 (and the user posted at least 5 questions), then throttle the account to a maximum of 1 question per day.

If the average is -3, throttle the account to a maximum of 1 per week. If the average is -5 (this means having posted for example 5 questions which an average of -5 scoring, which is pretty extraordinary) then don't let the user post questions for 30 days. The number obviously can be tweaked.

This should include deleted questions.

*Everything should be both account based and IP based.

Maybe you should add a throttle for new questions based on the average of votes of the user's past questions*.

For example, if the average scoring of questions asked in the last 30 days is -0.5 or less (and the user posted at least 2 or 3 questions), then throttle the account to a maximum of 1 question per day.

If the average is -3 or less, throttle the account to a maximum of 1 per week. If the average is -5 or less then don't let the user post questions for 30 days. The numbers obviously can be tweaked.

This should include deleted questions. Maybe in calculating the average cap the minimum score to -6, so users won't get suspended for a very long time if they post a single exceptionally bad question.

*Everything should be both account based and IP based.