If a user creates a custom greetings topic, it displays on the 'Show me Everything' list.
There is a column on sys_cs_topic that controls this behavior. You can hide the topic by changing the value in the column for that particular topic.
Release or Environment
This is caused because any custom topic that is created is automatically set to 'Is Topic Visible' to true. This column on out of Box 'Greetings' topics is set to false.
1. In the application navigator, go to sys_cs_topic.list
2. Add the 'Is Topic Visible' column to the list.
3. Change the value to 'false' for the custom/personalized greetings topic.
This should resolve the issue.