Hey, Dan from React team checking in. 
There’s an official tool called Create React App that we recommend people to use.
It would be great if project bootstrapped with it could work on Glitch.
This is not related to hot reloading per se, but I bumped into the same problem.
If you open this project built with Create React App, you’ll notice reloads are very slow.
If you look at the logs, you’ll notice this is because Glitch stops the server on every file change:
Compiling…
5:31 PM
Starting the development server…
5:31 PM
But Create React App development server assumes incremental updates. If only Glitch didn’t kill the devserver, reloads would be so much faster. Create React App already takes care of recompilation on file change.
I imagine the solution as adding another checkbox called “Restart Server on Changes”:
Now, to make it clear, there’s very little in a product that annoys me more than options or checkboxes. But in this particular case I feel like it’s making usability much worse, and with the shift to bundler-based workflows, it’s going to keep coming up, whether people are using React, Angular, Ember, or something else. It would be great to address built-in watcher paradigm in the UI directly, especially since workarounds like watch.json aren’t particularly discoverable.
Thank you for considering this request!