I salt my watermelon as well. Also salt my apples sometimes, and always put salt and pepper on cantaloupe and honeydew melon.
My father always salted his melons. His idea was that, in hot weather, more salt was advisable. It actually was very tasty.
On the other hand, MIL would pick beautiful tomatoes from her garden, slice them for lunch and sprinkle them with sugar before serving. That made me cry a little.
No no SALT goes on tomatoes, not sugar
I have never sugared tomatoes.
However, I grew up with honey on toasted tomato sandwiches. And salt, pepper, and mayonnaise.
I also grew up with jam on toast, regardless of what went on top - scrambled eggs, ham, cheese... I still sometimes crave strawberry jam, garlic sausage, mayo, and cheese on white buns.
As a kid, I would eat salt straight out of the salt shaker. I finally quit sometime in college. I had enough of a salt habit that I once tasted the leftover salt/baking soda mix my mother would use for scrubbing the stove top. After that, I would mix it for myself.