Sayer

Halliday (1994: 140):

Behavioural Vs Verbal Processes

Halliday & Matthiessen (1999: 514):

Language itself, of course, is a form of human behaviour, but "languaging" constitutes, for the grammar, another distinct type of process, that of "verbal" (or, better, "symbolic") processes. An act of saying is not simply externalising inner events; it is actively transforming them, into an event of a different kind. It then resembles other semiotic events, many of which do not require a conscious information source (your diary says you have a denial appointment, the light says stop).

Verbal Processes = Symbolic Processes

Halliday & Matthiessen (2014: 303, 304):

‘Saying’ has to be interpreted in a rather broad sense; it covers any kind of symbolic exchange of meaning, like the notice tells you to keep quiet, or my watch says it’s half past ten. The grammatical function of … the notice, my watch is that of Sayer. 

… unlike ‘mental’ clauses, ‘verbal’ ones do not require a conscious participant. The Sayer can be anything that puts out a signal … In view of the nature of the ‘Sayer’, verbal processes might more appropriately be called ‘symbolic’ processes …

The Particularistic Model Of Participation-In-Process: Topology

Halliday & Matthiessen (1999: 153):

What we find, if we try to take in the picture as a whole, is a kind of focussed model in which the essentially human processes of consciousness, and the prototypically human processes of symbolic action, constitute the experiential centre; while the two other types of figure, that of doing on the one hand and of being on the other, lie on opposite sides of this centre: the one (doing) lying towards the pole of the concrete, with experience construed as ‘this impacts on that’, the other (being) lying towards the pole of the abstract, with the experience construed as ‘this is related to that’.

Sensing & Saying: Conscious Processing & Symbolic Processing

Halliday & Matthiessen (1999: 153): 

The general motif of figures of sensing is ‘conscious processing’; that of figures of saying is ‘symbolic processing’.

The Categorisation Of Experience That Underlies Figures Of Saying

Halliday & Matthiessen (1999: 153):

In figures of saying, the Sayer is the symbolic source: prototypically human, but not necessarily so (e.g. the instructions tell you to switch it off first). The Process is symbolic; but here too there is a subtype of figures of saying that imparts a similar sense of action and impact, those where the Sayer ‘does something to’ another participant by means of a verbal process, as in Don’t blame the messenger, Everybody praised her courage. We refer to this participant as the Target; and again, we may note a partial analogy with figures of doing (though only partial — for example, such figures cannot take a resultative Attribute or other representation of the outcome.

Symbolic Processing And Projected Symbolic Content

Halliday & Matthiessen (1999: 129):

… the projecting figure represents symbolic processing, processing that brings another figure into symbolic existence. Figures of symbolic processing involve the symbolic process itself (thinking, saying etc) and a participant engaged in the symbolic processing, as in ‘Symboliser’: she + ‘Process’: said/thought —> that he had left. The projected symbolic content is either a proposition (she said/thought —> he had left) or a proposal (she asked him —> to leave; she wanted —> him to leave).