Hm not sure. Basically, I think Submissions graph is cool because the Y axis is points and it's fun to see your most popular posts. I'd like to see that same visualization applied to the comments graph (so replacing replies with points as the Y axis). Sometimes you can have a really popular comment that doesn't get many replies because people agree with it. Replies feels more like an indicator of controversial-ness, which are posts I'm probably not going to look as fondly back on.