1) Use real bold to replace synthetic SimSun bold; 2) Regular SimSun/中易宋体 can also be substituted; 3) Reassign font fallback list (Latin AND CJK). Browser serif/sans settings are overridden; 4) Use Latin fonts for Latin part in Latin/CJK mixed texts; 5) Fix fonts and letter-spacing for CJK punctuation marks.
If you think this script is breaking Greasy Fork's rules, please report it for removal.