Would one consider the terms "is not", "am not", "were not", etc. valid E-Prime? After all, no implication of indentity occurs; only the logical fact that no such identity exists.
Edit: I've noticed that the terms "is not", "am not" and "were not" do not have the formattng applied to the usual usages of the verb "to be". I assume this implies the validity of the negative copula in E-Prime...