I was about to write the spacebar thing off as my being tired last night, because I tested for some minutes and couldn't get it to happen. However, I clicked back in after alt tabing and indeed it actually opened and closed the pause menu, several times in a row, with spacebar. Then it went away shortly after. That, or I'm haunted with some strange ghost...
Ha! Found it. When you click Resume(or any other) button in the pause menu, it grabs focus. If you press spacebar, it will press the button and close the menu. Then, while the menu is closed you can still press the button with spacebar, and because Resume is a toggle and not just a close, it will toggle the pause menu with spacebar, including when you shouldn't like when viewing a lore page. Good to know I wasn't going crazy.