Ironically, your comment is itself a perfect example of discussing an idea. In fact, I would argue that discussing people and events as proxies for the discussion of ideas does not fall foul of the maxim.
One thing is to discuss how candidate X chooses to dress, whether candidate Y cheated on their partner, or how candidate Z looked so stupid in that incident yesterday. Another very different thing is to discuss candidate X's personal background (and how it makes them more likely to understand a given issue), that candidate Y does not practice what they preach (and probably cannot be trusted), or that candidate Z has owned up to their screw-up yesterday (and self-criticism is a good trait for leadership).
One thing is to discuss how candidate X chooses to dress, whether candidate Y cheated on their partner, or how candidate Z looked so stupid in that incident yesterday. Another very different thing is to discuss candidate X's personal background (and how it makes them more likely to understand a given issue), that candidate Y does not practice what they preach (and probably cannot be trusted), or that candidate Z has owned up to their screw-up yesterday (and self-criticism is a good trait for leadership).