This article analyses public debate on Twitter via network representations of retweets and replies. We argue that tweets observable on Twitter have both a direct and mediated effect on the perception of public opinion. On this basis, we show that through the interplay of the two network representations, it is possible to investigate which opinion groups on the platform primarily shape public opinion, and which ones remain silent to a disproportionate degree. The method is employed to observe public debate about two events: The Saxon state elections and violent riots on New Year's Eve of 2019 in the city of Leipzig. We show that in both cases, (i) different opinion groups exhibit different propensities to get involved in debate, and therefore have unequal impact on public opinion. Users retweeting right to far-right parties and politicians are significantly more active, hence their positions are disproportionately visible. (ii) Said users direct their replies primarily to other opinion groups, hence act more confrontational, while the contrary is not the case.