The argument about salt or sugar is a rather old one.

When people used to grow their own, it was observable that in certain soils, and/or with unusual seasonal variations in moisture, watermelons can have a slightly "bitter" taste (a bit like the occasionally bitter cucumbers from the next patch), and a bit of sugar made them more palatable. (Even when the melons are "off" in taste in this way, salt actually kills the off-taste about as well as sugar, in my experience.) So far as I was ever able to determine, this was a very "localized" phenomenon, so using sugar on watermelons was mostly a "family thing" since only the melons grown in specific (garden?) plots of land would benefit consistently.

For melons that matured normally, a little salt "draws the sweet" and actually may "sweeten" the taste of a "normal" melon (if that's how you like it) sufficiently.

In the climates where watermelons grow best, nearly all those who actually work the plots probably have at least a slight "salt deficit" so adding some (sometimes a lot) on the watermelon is a common, and possibly good, idea.

Since almost the only place we can now get watermelons is from the supermarket, and those have almost no flavor at all (especially the "seedless"** kinds), it's impossible to argue much with about anything someone wants to add to their own slice.

I generally use a fair bit of salt, but maybe I'll try some barbeque sauce or Thousand Island dressing on one. It probably wouldn't hurt on the crap we've been able to get recently.

** The "seedless" ones still have about the same number of seeds. They're just too #@$!# little to SPIT.

John