The rules are arbitrary, and the system they generate is self-contained. Readers can be positioned to read through a sign system. The quibble is not with the limits on the possibility of attaining full access to some represented world. The quarrel is with the assumption of some uniform space in which a global system operates. Readers read books.
Some readers read both electronic and hard copy forms of text.
Some readers even communicate with other readers about their readings. Electronic Signs in its invocation of Pierce's notion of interpretant fails to observe that Pierce brings the work of signification to rest in community. One of the important stops in the endless chain of unlimited semiosis is the consensus of a community of interpretants. This does not lead to the picture of a lone reader enclosed by single represented world. A textual instance is not simply a system.