[angus-prune]

As many equivalently ambiguous examples could be formed with he or she, particularly when there are more than one person of the same gender.

There is ambiguity in all natural language and we work around it quite effectively with either assumed knowledge or phrasing which removes the ambiguity (while often adding other ambiguities which aren't plausible so ignored).

Stallman says himself that he can understand his examples, and a couple aren't even ambiguous. He's adding in hypothetical other people to make them ambiguous.

Stallman has highlighted a problem with English and happened to use singular they as an example. He hasn't highlighted a problem with singular they.

[tom_]

The weird thing is that we seem to do just fine with singular you, so it's not obvious - at least, not to me - why singular they would be such a problem.