Before revision:  Second, we study the differences between these two communities. /r/ Coronavirus is recommended as the official community for COVID-19 on Reddit, while /r  /  China _flu adopts a loose moderation practice. As a result, we observe that these two communities are gradually growing apart and more extremism is being found in /r/China _flu.
After revision:  Second, we study the differences between these two communities. /r/ Coronavirus is recommended as the official community for COVID-19 on Reddit, while /r / China flu from January to March were more likely to leave, while those who started in later months tend to remain highly "loyal". To understand this difference, we develop a movement analysis framework to understand membership changes in these two communities are gradually growing apart and more extremism is being found in /r/China _flu.