Hiding weak information in a complex presentation aid is not ethical. Ethical communication involves presenting accurate and complete information to the audience. By intentionally hiding weak information in a complex presentation aid, Janet is deceiving the audience and not providing them with the full picture. This undermines the trust that the audience has in the speaker and can lead to negative consequences if the deception is discovered.
The fact that no one remembered the presentation aid does not necessarily say anything about the speech as a whole. It is possible that the speech was otherwise strong and engaging, and the audience simply did not notice the weak information. However, it is also possible that the audience was not engaged enough to pay attention to the presentation aid, or that they did not have enough context or background knowledge to understand it. Regardless, the fact that no one remembered the presentation aid does not excuse the unethical behavior of hiding weak information.
If I were Janet's boss and found out what she had done, I would consider her behavior unethical. While it is important for speakers to be strategic in their communication, it should not come at the cost of deceiving the audience. Janet's behavior undermines the trust that the audience has in the organization and damages the reputation of both the speaker and the company. As her boss, I would need to address this behavior and work with Janet to ensure that she understands the importance of ethical communication and takes steps to improve her future presentations.