Here's a font. It has a size and a weight. Lines of text have a height.
You will love them.
Love them, dammit!
All you can do with iA Writer is write. It has no opions and no settings. It's incredibly hard to make any writing app work without deferring design decisions to the user. We and 999 out of 1,000 users would like to keep it as it is.
I guess it's good the market for text editors isn't competitive.