Should punctuation marks be underlined, bolded or italicized?

I have read previous threads that punctuation marks should not be underlined at the end of a sentence unless other more specific rules apply (e.g., titles). My question is what to do and what to underline/bold/italicize when two punctuation marks are used?

For instance, should the following sentence underline/bold/italicize to the last "t" in Significant, to the period, or to the last quotation mark? I would assume the quotation mark would not be marked as underlined based on previous forum threads read indicating NOT to underline punctuation marks, although it doesn’t appear correct when bolded. I am assuming there must be different rules for underlining, bolding, and italicizing, with italicizing and bolding being more in line with each other. The following examples are in bold, but the answers might be different if the same examples were underlined.

Bolded Examples

Example 1 (Bolded to the very end of the quotation mark): Note, if an examinee only has an error, all other questions should be marked as “Significant.”

Example 2 (Bolded to the period): Note, if an examinee only has an error, all other questions should be marked as “Significant.”

Example 3 (Bolded to the letter t): Note, if an examinee only has an error, all other questions should be marked as “Significant.”

How about the same sentence underlined? Which one would be correct?

Example 4 (Underlined to the very end of the quotation mark)

Example 5 (Underlined to the period)

Example 6 (Underlined to the letter t)