Very useful graphs. Gives us a good insight. Is there a way you can get the total number of Accounts on Steemit quickly?
It takes a long time to get to the 70s club!
Will it be possible for you to make a separate viz for this showing how many months people took to cross 70s. Most of the people are not aware that the difficulty increases exponentially and they assume it will be a linear process.
The two easy ways you can get stats on steemit is to look at steemsql or steemdata. Both of these sources let you see the number of accounts quickly.
On your second point it would be interesting to look at how reputation has grown over time for some users but that data is not easily available. I do plan on tracking this data going forward so it should be possible in the future and a picture will begin to emerge.