Reviews and comment are moderated on MacUpdate. There are a number of reasons why a post would get removed:

• The post used inappropriate language
• You're a developer posting positive star rating reviews of your own app
• You posted multiple comments and reviews on the same app, same version
• Your review or comment isn't about the app itself but about something else unrelated
• Your post contained blatant mis-information that was not true

View out Community Guidelines for more details.