Better checking of namespace

We're aiming to get this into release-238 for release tomorrow. This PR is to dev, which will then be cherry-picked into the release branch.

https://wikia-inc.atlassian.net/browse/VE-1397
I understand. This is a contenteditable problem, not VE. Contenteditable, unlike <textarea> renders html and may contain redlinks. Clicking the redlinks will bubble to the body and we'll try to handle them as normal redlink clicks.