It seems that when working with semi-large datasets, (I have 204 points) the scatter chart does not use up all of the horizontal space afforded to it. This makes for very compact hard to read charts and visually looks very bad. I am using chart.js latest (v 2.4.0) on macOS and Chrome. Here is a link to the codepen where you can see exactly what is happening, along with a version of my dataset to test with.
Please let me know if you need any other details.
EDIT: Based on more reading of closed issues, this could be a problem with a calculation of how far apart to space each datapoint based on the width of the canvas. See #248