How to stop obsidian from popping up a character when holding a key

If you're in vim mode, and you hold l to move to the right, mac OS X pops up a character selection box that is annoying, useless, and distracting in this context (but might be useful elsewhere)

To prevent this, set a default:

defaults write md.obsidian ApplePressAndHoldEnabled -bool false

If you would rather prevent it system-wide:

defaults write -g ApplePressAndHoldEnabled -bool false

Solution via this thread