The big thing missing on repl.it is to use visual studio code instead of their own editor (think like Stackblitz), that would really be a game changer to be able to use one custom key-shortcuts, to use vscode plugins and so on.
And as much as I like vscode and the team behind it, it doesn't seem smart to tie your core tech to a project under the control of MSFT.
With regards to extensions you can easily imagine a vscode-replit bridge.
Finally, we came up with a novel approach to IDE/window management that we think people will be excited to write extensions for when we open it up: https://repl.it/blog/ide
Repl.it, with all the features we added, still loads with an editor and a console and a huge green run button. Most users, even those very new to programming, intuitively get it.
>the code is not really under the control of Microsoft in the sense the is open source and in the worse case scenario you create a fork from the latest build, which is already pretty stable.
I'd like to see a 10 person startup maintain a monster codebase fork like that. I agree it's a nice insurance policy, but it just not realistic.
Anyways, your original feedback is well taken and we'll make sure to create some compat layer :-)