Questions about Best-Practices are general and can have many acceptable answers.
Shouldn't they be marked as Community Wiki by default?
The Community Wiki definition is all about collaborative editing, and I think the idea is mainly intended for situations where there is no clear or definitive answer. Some "best practices" questions do have a definitive answer; some don't.
In some cases when people say "best practices" they actually mean "my practices". I think the antithesis of "best practices" in this context is "anti-pattern". Both terms are sometimes used by people who just have a strong view.
So I would say that "best practices" is not a strong enough indicator - it depends on whether there is a definitive answer or it is a subject of debate.