- * Callback function for warnings, errors, and fatal errors as they
- * occur in the compilers libroff, libmdoc, and libman.
+ * A punctuation delimiter, used only in mdoc(7) documents, is opening,
+ * closing, or "middle mark" punctuation. These govern spacing.
+ * Opening punctuation (e.g., the opening parenthesis) suppresses the
+ * following space; closing punctuation (e.g., the closing parenthesis)
+ * suppresses the leading space; middle punctuation (e.g., the vertical
+ * bar) can do either. The middle punctuation delimiter bends the rules
+ * depending on usage.