Can I use Apple's San Francisco font (and other fonts) in my own text editor? Can I use Apple's fonts in my Atom text editor. This seems to suggest I can't. Can anyone confirm this?
I know, of course, Apple has no way of finding out if I do. I just don't want to use it if I'm not allowed to.
No.
As you mention, you can do it technically, but the license I reviewed appears to not grant anyone a license to use this work in personal projects. Some good people agree with me as well. As a developer, you will want to get good legal advice on licensing - what we think on this internet site isn’t likely to be prudent legal advice. Even if I was a lawyer, I’m certainly not your lawyer.
Read your legal agreement carefully. If you wish to license the typeface, you could ask Apple for (or your business manager to acquire) that license or how much they would charge for such a personal use license.