I bet you know the answer. Some will want the pristine poster without alteration, others will accept this "vandalism" and see an item with increased value. Unless the poster and signature(s) are of the same period, I am in the first group (apart from something vintage with a vintage-ish signature, like...a Lifeboat 1944 original dblw weight lobby still signed in 19...59 by T. Bankhead.