I just upgraded to 15063 and the watermark is gone. being so close to Creators update, these builds are pretty safe. But insider build 15063 is out in the wild on the fast ring
NOTE: I never knew this until fairly recent but, if you are an insider and somehow I have found a seemingly persistent issue that is fairly easy to fix. Usually people complain or have been about their PC not downloading the latest update. it will try and you'll get an error. I found out the issue:
type "regedit" into the cortana box and navigate to and delete the following registry key (its safe to do so)
the offending key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\RequestedAppCategories\8b24b027-1dee-babb-9a95-3517dfb9c552
delete the item labelled "8b24b027-1dee-babb-9a95-3517dfb9c552"
it appears it causes issues where by you'll get errors about not being able to download the update. for me, I can attest through deleting this key BEFORE I update my system to a new build and the update download errors ceased.
Link Removed