My response: "Lo siento, no hablo francés". WRONG! "Lo siento, YO no hablo francés." So my question is, since we generally drop 'yo' so as not to sound self-important, does that apply here? Or is 'yo' in this instance a mandatory clarifying object/subject? Or is the translation program just being picky? This may be three questions...
Using yo emphasizes that it's ME that doesn't speak French. It has nothing to do with self-importance and everything to do with emphasis. So dropping the yo is totally fine and you can report it next time you get the question.
I really don't get why duolingo so strongly insists on using the pronouns.