This is not strictly a DnD5 question, but I have not seen any other game where creators share rules interpretations via social media.
Mike Mearls's tweet got me thinking about about the value and strength of these suggestions:
Does the paladin’s Great Weapon Fighting style apply to the radiant damage dice gained from Divine Smite?
No – I'd rule the benefit applies only to the weapon's damage dice.
This is obviously against RAW, but on the other hand he makes very clear that this is only his opinion. So it is just a house-rule from someone who intimately knows the game.
Should we consider tweets when answering questions about rules? Or are they only recommendations?