The current use of overlapping line plots makes it difficult to clearly understand the probability that turnips would be a given price on a given day. In addition, the use of a line chart subtly implies that the price of turnips is a continuous function, which it is not.

A much more ideal visualization would be a box plot or a violin plot. Personally, I prefer box plots, because I find them more intuitive. However, @mikebryant, the maintainer of Turnip Prophet, stated that he preferred violin plots because they are more detailed.

I originally brought this issue up here.