Just now, half a day after posting an entry, I decided I'd like to use a custom entry permalink, so I updated https://brainwane.dreamwidth.org/94392.html to https://brainwane.dreamwidth.org/2017/02/27/english-tutoring-request.html. I thought, "I'll check whether this breaks the old numerical permalink, which people have already started passing around, and if so I'll switch back." But no! Both links work and now they both point to the entry! Someone thought about this scenario and made it so that my use case works fine. Thank you for thinking ahead and making my life easier, Dreamwidth!