New answers tagged call-to-action
You could also have a sticky element that expands into a form when clicked rather than redirecting to a new page.
I think this is a great idea; it saves space, lets the user get to it when desired, and increases engagement. To answer your questions regarding justification, simply look at Stack Exchange sites. Nearly everywhere you navigate to in the interface, the "Ask a Question" button persists. Something similar on your site should be effective, if implemented ...
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