[Fwirt]

For starters, Sublime Text is closed-source. A better parallel would be something like Neovim, which also is extensible with Lua. What draws me to Textadept over Neovim is that it's intentionally kept very small, which means it's very easy to understand and extend. Contrast with Vim and its massive manual. However, like Emacs, almost everything is fair game for customization. For example, I wanted minimap functionality, so I implemented it:

https://github.com/Fwirt/textadept-minimap

Textadept's biggest strength is also its biggest weakness: Scintilla allows for a lot of features that are nigh-impossible in the likes of Vim and Emacs due to their reliance on terminal behavior. However, Scintilla is not terribly well optimized and does not support GPU rendering, meaning that while there is very little bloat, Textadept can still chug in some edge cases. The most notable instance right now is large files with no line breaks (e.g. minified js libraries). Other Scintilla-based editors also suffer from this to varying degrees, although Notepad++ has some performance optimizations that seem to mostly mitigate it. Notepad++ is also Windows only and not as easily extensible.