Developer chatrooms (e.g., the Gitter platform) are gaining popularity as a communication channel among developers. In developer chatrooms, a developer (asker) posts questions and other developers (respondents) respond to the posted questions. The interaction between askers and respondents results in a discussion thread. Recent studies show that developers use chatrooms to inquire about issues, discuss development ideas, and help each other. However, prior work focuses mainly on analyzing individual messages of a chatroom without analyzing the discussion thread in a chatroom. Developer chatroom discussions are context-sensitive, entangled, and include multiple participants which make it hard to accurately identify threads. In this paper, we perform an in-depth analysis of the Gitter platform (i.e., developer chatrooms) by analyzing 6,605,248 messages of 709 chatrooms. To analyze the characteristics of the posted questions and the impact on the response behavior (e.g., whether the posted questions get responses), we propose an approach that identifies discussion threads in chatrooms with high precision (i.e., 0.81 F-score). The analysis of the identified results shows that inactive members responded more often and unique questions take longer discussion time than simple questions.