Non-breaking spaces are required to typeset French correctly, at least: https://en.wikipedia.org/wiki/Question_mark#Stylistic_variants https://en.wikipedia.org/

Non-breaking spaces are required to typeset French correctly, at least: https://en.wikipedia.org/wiki/Question_mark#Stylistic_variants 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.