The correct spelling for the phrase "comments up on" is /ˈkɒmənts ʌp ɒn/. The first word, "comments," is spelled with the letter "s" in the middle to indicate the /z/ sound. The second word, "up," is spelled with the letter "u" to indicate the /ʌ/ sound. Finally, the word "on" uses the letter "o" to indicate the /ɒ/ sound. This phrase is often used in online forums or social media to indicate that someone has replied to a previous comment.