In his Grammar of Spoken Chinese (1968), still the best grammar of Mandarin available, Y.R. Chao states that all clauses in Chinese are topic-comment, and there are no exceptions, though there are some clauses that only have comments, as in (1):

Put very simply, the structure of the clause has two parts: the topic, which is reference to some referent available for comment; and the comment, which supplies some information about that topic. Chao (1955, 1959) argued that word order is no…