I think it's fairly safe to assume that most of the character's text translates (at least partially) to their normal speech. The easiest example is that Karkat TYPES IN ALL CAPITALS, and is said to shout a lot. tAVROS, UH, TYPES IN,,,iNVERTED CASE, with lots of commas/pauses, and he's said to be lacking in confidence when he talks.
Comments on Profile Post by AetherArising