>Sublime uses a Python API, though the docs are also not extensive
But how extensible is Sublime itself? For example, in Emacs I can do network connections (e.g. Gnus). Will Sublime allow this? Can I make a Tetris clone in Sublime? Both are doable in Leo.
AFAIK Sublime gives you a full Python, including network access. The problem is that you're limited to a few predefined hooks where you can integrate into Sublime's UI, so good luck making it do something that doesn't boil down to editing text.
Is Sublime itself written in Python? Or is it mostly C++ with some Python hooks? If the latter, it'll be quite limited.
Leo is all Python, and you have access to all the internals. I'm sure there are design decisions in Leo that will make changing some aspects hard, though.
But how extensible is Sublime itself? For example, in Emacs I can do network connections (e.g. Gnus). Will Sublime allow this? Can I make a Tetris clone in Sublime? Both are doable in Leo.