Many apps and bots have similar commands, just flooding the chat by a lot of notices. For many bots, it's enough to display the tip menu, and all human messages are gone.
When people enter the chat, they see the last 10 lines except notices. Thus the flood bots won't hide a message from people who arrive after flooding.
In order to get the line out of everybody's view, best is to do two things:
1. Have a bot flood the channel - most of them do that all the time anyway, destroying most of the human communication.
2. Have 10 lines appear in the chat which are not produces by apps or bots. For example, writing 10 ordinary chat lines will do the job. Or having somebody tip 10 times.