  Existing text style transfer (TST) methods rely on style classifiers to
disentangle the text's content and style attributes for text style transfer.
While the style classifier plays a critical role in existing TST methods, there
is no known investigation on its effect on the TST methods. In this paper, we
conduct an empirical study on the limitations of the style classifiers used in
existing TST methods. We demonstrate that the existing style classifiers cannot
learn sentence syntax effectively and ultimately worsen existing TST models'
performance. To address this issue, we propose a novel Syntax-Aware
Controllable Generation (SACG) model, which includes a syntax-aware style
classifier that ensures learned style latent representations effectively
capture the syntax information for TST. Through extensive experiments on two
popular TST tasks, we show that our proposed method significantly outperforms
the state-of-the-art methods. Our case studies have also demonstrated SACG's
ability to generate fluent target-style sentences that preserved the original
content.
