Or does it only work on melee infantry?
It works on all infantry, including ranged infantry.
If you actually calculate its effective DPS, the Sofa does higher DPS than the Horseman against all Ranged Infantry.
I checked the encyclopedia of the game and came to the same conclusion as you. But my friend told me that sofa doesn’t actually have any bonus to ranged infantry.And I can’t use the computer now. Can you test it in game?
I test unit stats and stuff regularly, and I can definitely tell you it does its bonus damage just fine as intended.