Let us look at the sentences
I think, that man always errs. / I think that man always errs.
Does my punctuation officially suffice to clarify that the first sentence refers to a specific man, while the second refers to Homo sapiens? If not, how to improve the punctuation? I am not interested in rephrasing the sentence. It's just an example for a general problem.
I tried to clarify this using the internet, but failed to find the appropriate guideline.