The first character on a text input line cannot be a dot (‘.’) or an apostrophe (‘'’). If these characters appear at the beginning of a text line, put the zero-width space escape sequence (‘\&’) in front of them to escape them. On text lines, nothing else is special about punctuation, just use punctuation normally.
If one or more punctuation characters follow a macro invocation, put them at the end of the macro line, separated by blank characters from the preceding macro arguments and from each other. See the “Delimiters” subsection in the mdoc(7)
manual for details.
After the end of a sentence, whether it occurs on a text or macro input line, end the input line and start the next sentence on the next input line.
If a text input line happens to end with a punctuation character (for example, due to an abbreviation), but the sentence continues on the next input line, put the zero-width space escape sequence (‘\&’) right after the trailing punctuation character such that it isn't mistaken for the end of a sentence.