When starting Minecraft with a resource pack that contains a font with a resolution higher than the default (128x128), the text becomes very distorted and cut up. Switching back to a default resolution font will not fix this.

However, when starting Minecraft with a resource pack that contains a default resolution font, and then switching into a high resolution font, the text is not distorted and completely fine.

This issue can get annoying, because you have to switch to a 16x16 resource pack before exiting Minecraft in order to keep the text un-distorted.