I see that certain significant questions are protected by the community.
Can I 'flag' a question as significant enough for becoming protected?
Questions are usually protected when there is a slew of non-answers being posted as answers.
Protected questions have the additional restriction that new users are not permitted to answer the question. Unlike locked questions, they can still be edited, commented on, and voted on. You can even vote to close them.
Examples include:
Usually in such cases, the question will be protected by a mod, a high rep user (15k and up). The Community user will automatically protect any question where three answers posted by new users have been deleted.
You cannot simply trigger protection via a flag, however, as a real person must accept your request and follow through with protecting the question. However, if you believe a question should be protected, flag for moderator attention and someone will look at it.