The phrase "commenting up on" has various meanings, and its antonyms may vary depending on the context. For instance, if it refers to adding positive feedback or compliments, the antonyms could be criticizing, condemning, or disapproving. Alternatively, if it is used to express agreement or approval, then the antonyms might be disputing, disagreeing, or objecting. Conversely, if the phrase is used to describe someone who remains silent or chooses not to share their thoughts, the antonyms can be expressing, voicing out, or articulating. Therefore, it is essential to understand the precise sense of the word "commenting up on" to identify its valid antonyms accurately.