Currently the GH burndown chart does not show the stories added or removed after the initial plan. So if a sprint starts with several issues that comprise 16 story points (their committment), and then halfway into the sprint, the team decides to add 1 issue w/4 story points from the backlog, GH will redraw the graph in a way that shows the original committment as 20 story points, which actually the graph should reflect that 4 story points were added 1/2 way into the sprint.

This is misleading because id a team took on more they should get more credit for it or it can be used to help understand "why did our plan change"

Jeff Sutherland showed us how to do this in Scrum (which is also how some google teams do it) by showing a "Change in Committment" line to the story point Burndown chart. The Committement line stays at 0 if there are no changes, but goes down (into negative territory) if story points get added, and goes up if story points are dropped. GH would no longer redraw graphs with the line moving from 16 story points at the beginning to 20 points at the beginning if 4 points were added - rather GH would just draw the graph starting from the 16 points all the way down to -4 points. This keeps the ideal line intact as well as the original committment. See the I attached.