I use them when connecting a thought in between another thought—for example, what I just did right now—and then returning back to the original thought. I use a semicolon when connecting two related thoughts together*; LLMs tend to only use one em-dash, so I'm hoping that by using two of them instead—and a semicolon instead whenever an LLM would use an em-dash—there will be no confusion as to whether or not I'm human.