I set my grid sizes and exported, but all the icons felt a little higher than I wanted them to be in relation to their surrounding elements. I did some finagling in CSS, but found the results varied (sometimes wildly) between platforms.
After some fruitless Googling, I trudged through the font’s preferences and found the culprit: A rather diminutive baseline height value. In IcoMoon, this is under Preferences, then Font Metrics.
Here’s a quick example at the default height (6.25%):
Here are the same elements and icons, but with a larger baseline height (18.75%):
Lesson learned: If the icon font’s vertical alignment is off, adjust its baseline height before resorting to CSS tweaks.