I generated this by asking Claude to translate Kale Kundert's NestedText syntax definition for vim and reporting back what went wrong a dozen times. Tadaa!
From Sublime Text's command palette,
install NestedText.
Copy NestedText.sublime-syntax and NestedTextComments.tmPreferences
to the user packages folder,
which on Linux is usually ~/.config/sublime-text/Packages/User/.