I think this is the exact situation that diff comments exist for, right? If I don't use this feature, I have to copy over the code, the file, and the line number to the pull request. It's much easier this way.

The system query isn't there anymore. Historically, forms that had a System field would populate a dropdown full of system names. However, because there's 80,000 systems or so, this would cause pages to load very slowly even when the user didn't need the form. And when the user did need the form, the didn't need the entire list of systems because it was automatically selected for them.