A useful baseline is that the essential parts of an utterance are expressed, so listeners need not guess at its referent. Omission is an intentional departure from this baseline only when supported by context and a discernible purpose.
The discussion on printed page 133 treats mentioning the subject as the baseline. An omission therefore requires an indication and an explanation of its benefit. This does not imply that every stated subject is redundant or that every omission is eloquent.
Two questions must be separated:
Grammatical: what is structurally allowed and what has been suppressed?
Rhetorical: which formulation better suits this listener and circumstance?
A public announcement may need the named subject for identification, while a continuous conversation may benefit from avoiding repeated mention.