On the topic of zero anaphora and control in "topic prominent" languages, I've gone looking for some examples to illustrate what I meant and found some in Anaphora by Huang. In one part of the book he contrasts "syntactic" languages (e.g. English) with "pragmatic" languages (e.g. Chinese, Japanese), in a way which I think correlates quite strongly with the subject vs topic prominent distinction.
First, a short quote:
Huang wrote:
Let me start with the pragmaticness of anaphora in a pragmatic language. If we compare a prototypical pragmatic language (such as Chinese, Japanese, and Korean) with a prototypical syntactic language (such as English, French and German), we will find that anaphora in the former behaves in a more pragmatic way than that in the latter (see e.g. Huang 1994 for a detailed analysis of Chinese). More specifically, a pragmatic language seems to have the following characteristics as far as anaphora goes.
Anaphora in a pragmatic language
(a) Massive occurrence of zero anaphora
(b) Existence of pragmatic zero anaphors or empty pragmatic categories
(c) Pragmatic obligatory control
(d) Long-distance reflexivization
The crucial point here for the previous discussion is that zeros are widely used, and not in a syntactically restricted way. Multiple zeros can occur in the same clause, with different antecedents, not restricted to be the marked topic of a previous or matrix clause.
Naomi-wa Ken-ni 0 0 aisiteiru-to itta
Naomi-TOP Ken-to 0 0 love-COMP say-PAST
"Naomi told Ken that (she) loved (him)"
John-un Mary-eykey cenhwa-lul hayssta kulikonun 0 0 0 salanghanta-ko malhayssta
John-TOP Mary-to telephone-ACC did and.then 0 0 0 love-COMP said
"John called Mary and then (he) said that (he) loves (her)"
Compare the following for an example where, in a relative clause, both zeros can be either the head or an external topic:
Laoshi hai zhao bu dao [yi ge [0 keyi jiao 0 de] xuesheng]
teacher still find not one CL 0 can teach 0 REL pupil
"The teacher still cannot find a pupil whom (he) can teach"
Xuesheng hai zhao bu dao [yi ge [0 keyi jiao 0 de] laoshi]
pupil still find not one CL 0 can teach 0 REL teacher
"The pupil still cannot find a teacher who can teach (him)"
In the following, a zero in a subordinate clause is controlled by the matrix subject (and topic) in the first example, and by the matrix recipient (and non-topic) in the other. The choice is pragmatically driven, not syntactic rule driven, except for the fact that some restrictions come from the choice of matrix verb "promise" (specifically, the controller can be the subject or recipient, but not easily by e.g. the matrix location):
Kanja-wa isya-ni asita 0 kusuri-o nomu koto o yakusokusi-ta
patient-TOP doctor-to tomorrow 0 medicine-OBJ take COMP OBJ promise-PAST
"The patient_1 promised the doctor_2 that (he_1) will take medicine tomorrow"
Isya-wa kanja-ni asita 0 taiinsuru koto o yakusokusi-ta
doctor-TOP patient-to tomorrow 0 leave hospital COMP OBJ promise-PAST
"The doctor_1 promised the patient_2 that (he_2) will leave the hospital tomorrow"
In these "topic prominent" languages, the fact that the subject is
not the controller of zero anaphora does not mean that there is a replacement syntactic constraint that just replaces the word "subject" with "topic". Instead, the rules are a lot looser, and influenced not only by locally topic marked noun phrases, but referents that are discourse topical (even if they were last mentioned some time/distance ago), or just make sense in the context.
That's not to say that there aren't a small number of languages with something that looks like a grammaticalisation of a topic rule. I can think of a few languages which show things along those lines:
agreement with topics: Manambu
integration of topics into switch reference: Barai
integration of topicality into person paradigm: Algonquian languages (proximate)
But these are very different to the kind of topic prominence described by Li and Thompson for languages like Chinese and Japanese.