Seems like that might work. If I’m understanding it right, it still looks like you’d have to enter the data in the xxx,xxx,xxx.xx format. But that would flip the display of it around to use commas in the decimal place.
They’re using another library to handle formatting rather than trying to just do a string replacement which is good honestly but you’ll need to include it in the page as well.
As for implementing it inside the plugin you’d want to probably call the code using an action hook.
Maybe this one: m_chart_after_chart_args
Then you could modify the chart settings to use the library when rendering the numbers.
Still yes, pain in the neck Chart.js doesn’t already support this stuff natively.
Chart.js is still fairly young I think and it’s just missing some features like this. Highcharts already includes native comma decimal support. If you aren’t working on a commercial project that would probably be an easier choice:
https://github.com/methnen/m-chart-highcharts-library/