overline/underline issue not resolved

Created by: IMACS-Iain

https://github.com/mathjax/MathJax/issues/2701 is closed but not resolved in 3.2.0.

\overline and \underline are not visible ...

... on Firefox in Windows 10 v20H2 and v21H1, underline and overline not visible at 90% or 120%; ... on Firefox on Ubuntu 21.10, underline and overline not visible at 80%, 100% (but visible at 110+%)