I just remembered that Derrida had something to say about signatures (as in actually signing your name on a piece of paper, not in some metaphorical sense) as an interesting genre of text. They have binding consequences in the real world, so I guess that's the 'presence'/'speech' side of things, and also they have to be recognisably 'the same' every time, so that's the 'iterability'/'writing' side.
OK, yeah, it's in Signature Event Context. I'm not going to try very hard to work through this today, but this is the quote I was thinking of:
In order to function, that is, to be readable, a signature must have a repeatable, iterable, imitable form; it must be able to be detached from the present and singular intention of its production.
He's responding to Austin's How to Do Things with Words which I've never read and don't know much about, but I know it's about speech acts, speech as having consequences out in the world rather than making assertions. Signatures would fit into that category well.
This is a mildly interesting linguistic observation:
We also speak of different or remote places communicating with each other by means of a passage or opening. What takes place, in this sense, what is transmitted, communicated, does not involve phenomena of meaning or signification.
Interesting because it's similar to what Brian Cantwell Smith would call the 'bumping and shoving' layer of pure causal interaction, with no 'meaning' layer on top.
I can't be bothered to make any more effort with this at the moment, but it looks promising enough that I might go back to it.