4.4611 But tautology and contradiction are not nonsensical [unsinnig]; they belong to the symbolism, in a way similar to that in which “0” belongs to the symbolism of arithmetic.

They are bedeutungslos, presumably, referring to nothing, and they are sinnlos (by 4.461). But not, supposedly, meaningless. My translation is based, partly, on Wittgenstein’s remarks on p. 49 of his Letters to Ogden. (Or it was--I just changed "meaningless" to "nonsensical" without re-checking what Wittgenstein wrote to Ogden.)

Mounce (p. 43) says that Wittgenstein means that tautologies and contradictions say nothing (about the weather, e.g.) but nevertheless are not gibberish. They are not gibberish because there are rules for constructing truth tables that yield tautologies and contradictions, but not for gibberish. Also, tautologies and contradictions “show something about the nature of logical structure. Thus ‘p . ~p’ says nothing, but it shows something about logic that this cannot be said, or rather, that these signs when put together say nothing.” (What does it show?!) Mounce again: “In ‘p . ~p’, one might say, is revealed a disintegration of sense, but the value of ‘p . ~p’ is that the disintegration is revealed by means of it not to be arbitrary. One is aware, by means of it, of rules which reflect logical form and that enable one to construct out of the symbols which constitute it propositions that do say something.” (Is such a thing thereby revealed? Was it not already apparent? Could we understand ‘p . ~p’ unless we already grasped the rules of logic of which it supposedly makes us aware? Maybe it makes us more aware, or reminds us of what we already knew, but I’m not sure. And don’t the rules of logic, by which we construct truth tables, for instance, also mean that anything else is gibberish? So there are rules for constructing gibberish, namely (violating) the rules we must follow if we are to make sense.