Is signing your name a language act?
Basically, yes. I mean, you’re writing, right? There’s a bit of identity verification going on too–signatures are difficult to forge–but it’s not terribly robust. Traditionally if you’re illiterate you’re allowed to just draw an “X”. And the degree of forgeability or indeed legibility is entirely up to the signer. I, for instance, always start to sign my name with the best of intentions, but tend to lose interest about halfway through so that the “McNeill” disintegrates into a random thicket of spiky verticals. My wife’s signature consists of a blobby thing up front that conveys the general sense of being a capital cursive letter followed by a gently sloping unbroken horizontal line. It is completely illegible, not because it’s messy, but because it’s too uniform to count as writing. But she produces it with a visible, dramatic flourish, which, when you think about it, is the point.
Signing your name is an illocutionary language act. Like saying “I do” in a wedding ceremony, the point is the performance of the act itself, not any information it might convey. However, in a wedding ceremony you at least have to say “I do” audibly in order for it to count. For the illocutionary act of signing to occur, it is enough to pretend to write your name. (I say pretend because my wife and I are both perfectly capable of producing legible cursive versions of our full names; it’s just not worth our while to do so on every credit card slip.) These days there are even various signature-collecting electronic tablets–at checkout stands, in pharmacies, and carried by UPS delivery people–on which it is literally impossible to sign your name legibly even if you want to. Using a stylus on a awkwardly tilted screen produces a result that at best approaches what you could do with your non-dominant hand. Technology and custom has backed us into this odd corner in which we are obliged to be momentarily incoherent.