>How can you migrate a sub when other people on reddit can still use it?
there were still people on Digg for over a decade after the "digg migration". I think you're taking the term a bit too literally.
besides, migrations in software work the same way. You don't cold turkey drop the old tools. You make bridges, start weaning people on new tools, and phase out the old. That's the concept behind deprecation models.
No subreddit can fully move. Reddit is too popular for everyone to leave. A mod can start a new place but if they threaten the the sub itself like going private or not allowing posts the company can just open it with new mods.
there were still people on Digg for over a decade after the "digg migration". I think you're taking the term a bit too literally.
besides, migrations in software work the same way. You don't cold turkey drop the old tools. You make bridges, start weaning people on new tools, and phase out the old. That's the concept behind deprecation models.