“Or so he says” is a reminder that I’m just one person. So whatever you read, you can remember it’s limited by my own knowledge, expertise and experience. This is especially important when I talk about mental illness. If you’re learning about mental illness from me, I want it to be clear that people experience different things, even with the same diagnosis. I can only really speak about what I experience, and describe what I’ve learned.
“Or so he says” is also a joke. When I describe something I’m skeptical of, I have habit of adding “or so they say” at the end. If I don’t say it, I definitely think it. It’s only fair I do it to myself!