I was trying to understand what is being explained at 

I understand some parts of the explaination.  I am unsure of the Coefficient fo determination section, to me it seems to sugget that between about 5 to 10% of the change in the dependent variable can be explained by the indicator?  And I'm not sure if this ‘L’ shaped curve is good or bad?  Then they say they make a number of ML models using the sentiment indicator and they seem to not significantly outperform the benchmark in the ‘out-of-sample’ area.  So to me it seems the use of the sentiment indicator seems poor and entails quite an effort to get to a final working implementation.