I agree.  I can understand this notice in the main menu, but all the time during the game seems a bit bizarre.  Are the devs afraid they'll get screenshots and not know what version of the game they're looking at?  This doesn't seem like a great solution to me in that case.  Maybe a much smaller version watermark?

I do appreciate the effort it takes to make this game and how annoying uninformed bad reviews are.  But given the fact that the game is early access whether you're playing insiders builds or the general release version on steam, the most appropriate and sensible thing to do (especially if one goal is to head off bad reviews) is to put this text in the main menu of ALL builds, including the general ones, and to drop it during gameplay.  I can't comprehend the purpose of keeping this onscreen all the time.

Is there a way to make the watermark appear on any screen shot made?

Either when the prt scrn or ctrl+v buttons are pressed?

This would seem to be the solution for the problem of needing Streamers to emphasize this is EA and some who cannot play with a warning on their screen.