The issue came up about 3 years ago. Somebody quoted a passage from the W3C (sp?) website that demonstrated that a closing P tag is *not* required.
Maybe they backpeddled in the updates since, but it was not required a few years ago. Plus it is dumb extra typing and clutter, brought to us by the same people who invented that f*cken semicolon no doubt. I think of the P tag like an infix operator, such a plus sign in math or "." in Perl or "&" in VBscript.
So shuv your cackling where stellar photon radiation does not reach.