I can't really think of a definition of Not a Trope
other than just copying on People Sit on Chairs
and Too Rare to Trope
Something along the lines of:
"Everything that happens in various media is not tropes. A lot of things simply don't have any meaning to them, and just happen because the laws of reality are followed, or just events that just happen to further the plot, but have no meaning outside that. There are also some things that do have meaning, but there's no pattern of use in other works that makes it a storytelling convention.
"On this site, we also have things that aren't strictly tropes, but are still treated as such. Game mechanics is one such example. There are also areas where we have interesting information, like Useful Notes
, but these are not tropes at all."
Better than nothing, but can be improved a lot. Or not used at all, if someone writes something better.