"...we can easily demonstrate that reading reddit is a skill that develops and changes over time..." Actually, you've failed to demonstrate that. A better test

"...we can easily demonstrate that reading reddit is a skill that develops and changes over time..." Actually, you've failed to demonstrate that. A better test would be to record first time visitors and then come back after they've become long time users and record again. That way, you could rule out the mitigating factor that you mentioned earlier in the article: "...indicating that either only certain types of people become redditors, or that the veterans’ reading patterns had changed..."