It turns out that both the full model and base model performed comparably on recognizing implicit discourse relations without event or coreference constraints, with 407 vs. 402 discourse relations correctly predicted by the full model and the base model respectively.
the overall performance gains achieved by the full model are mainly from better resolving implicit discourse relations with constraints, and as shown in Table 5, the full model made 24 less errors than base model for predicting such implicit discourse relations.