…or fix the non-Unicode compatible systems that are consuming the commit messages and breaking? If they fail with an nbsp then they’re probably also going to fail with more obviously useful non-ASCII characters.
How often are non-breaking spaces purposely inserted vs accidentally? And the tools might handle them fine but will produce strange results or errors. An example is inserting a non-breaking space in a document or string. It will prevent word wrap, which might not have been the user intent. A linter that requires these spaces to be explicitly set in encoded form would avoid these issues.
Non-breaking spaces are required to typeset French correctly, at least: https://en.wikipedia.org/wiki/Question_mark#Stylistic_varian.... The accidental insertion of non-breaking spaces is a possible issue, and it's a bit harder to detect than other typos, but it's also probably not as bad as other typos. Overall I think it's a bit hard to make the case that they should be disallowed.
I was forced to gain very intimate knowledge of a web based rich text editor that would use non-breaking space characters as markers to monitor current user selection.
