the "namespace" button is unintuitive, and kinda hidden. it is also non standard UI design to put controls at the bottom or scrollable list.
the "filters" form is a form, and should behave like a form: all controls in static locations, and scrollable lists should only contain items of same kind.
same comment applies to "tagged edits" too, but this button is much less useful (for me) than "namespaces", which is a first class citizen, probably as useful as all other filters put together...
funny thing is, the form _has_ the marginally useful "highlight results" button like a form. the namespace and tagged edits buttons should be as prominent, if not more.
peace.