Spacing between italic characters and left/right brackets

When typesetting $[a,b]$ one obtains with MathJax version 2 and with MathJax version 3.0.1. This seems to be dependent on the character next to bracket being italic. Checked with both Firefox and Chromium on Linux. To see this in a live web page check: https://cdi2tp.math.tecnico.ulisboa.pt/test https://logrus.math.tecnico.ulisboa.pt/test