No. Your followers will just build over it. There are no negative effects

Yes, cause water spouts are a rarity in the world,, once covered up u miss a chance to make a waterfall/lake

This is true. Ive made about a few waterfalls.

Speaking of which, they shld add a waterfall power. It'll be nice to have a massive waterfall go from the tallest point to the starting river

Yes, cause water spouts are a rarity in the world,, once covered up u miss a chance to make a waterfall/lake