Summary:

The word si means "this message", in particular referring to the physical manifestation of the message in which it appears, and it is central to many communication-related phrases. (With the generalizer -ka, sika refers to a message in the language in general.) The word/morpheme for effect is -fe, and the word which takes effects back to their cause (reversing -fe) is -r-fe. This gives us the first person (more precisely "the cause/creator of this message"), sirfe.

Rather than immodestly referring to the listener as effects of the message, sife (which assumes they agree with the contents entirely), we would use -fa, which is a weaker version of -fe that suggests more awareness of an event instead of substantial affect. This makes the approximate second person translation sifa. (Conversely, to refer to oneself as sirfa implies one didn't have much control over the message.)

The third person generally refers to something outside the conversation or a particular message within it, i.e. something other than (-ke) something related to (-ki) the message (si), giving sikike. siki refers to people directly involved in the transmission/conversaion, since they are related to the message's form (being the start and end points in some sense).