Attracting new members is vital to the health of many online communities. Yet, prior qualitative work suggests that newcomers to online communities can be disruptive – either due to a lack of awareness around existing community norms or to differing expectations around how the community should operate. Consequently, communities may have to navigate a trade-off between growth and development of community identity. We evaluate the presence of this trade-off through a longitudinal analysis of two years of commenting data for each of 1,620 Reddit communities. We find that, on average, communities become less linguistically distinctive as they grow. These changes appear to be driven almost equally by newcomers and returning users. Surprisingly, neither heavily moderated communities nor communities undergoing major user-base diversification are any more or less likely to maintaining distinctiveness. Taken together, our results complicate the assumption that growth is inherently beneficial for online communities.