I was hoping that no one would take the Guardian obit seriously. Derrida never said anything even resembling "texts can mean whatever you make them mean." (I'm pretty sure Nietzsche never said that either, but alas.) He said that, in order for language to even function, there has to be a certain kind of play in it--like the play in the parts of a machine. That play has limits and functions as a limit for interpretation, but not the only one, because the play involved in any text is partly historically circumscribed. It is an utterly sensible position: texts don't mean just anything, but don't just mean one thing, either. And like Foucault (though I wouldn't push this analogy), he ascribed much of the limitation on interpretation as grounded in micropolitics.
It is easy to mis-state Derrida's importance. But two things stand out, in my mind. First, the simple gesture of displacing the values of "center" and "margin" in literary and cultural studies had far-reaching consequences. It was on the back of this kind of argument that gender, sexuality, class, race, and disability became privileged tropes of cultural studies in the 1990s. And for the most part, for the better, in my view. Second, if we just think of some of the big names in African-American studies (Henry Louis Gates, Jr.), postcolonial studies (Said, Spivak), and queer theory (Judy Butler), all of them were students of Derrida's. And his influence on the shape of the fields was even greater.
Christian