Everyone is slightly bipolar, amirite?

Umm...not really.

The whole point of calling it bipolar is that it is two opposite poles/ends of the mood spectrum. Yes, everyone has ups and downs, but not to the extreme levels of mania and depression that people with BPD experience.

I know you said "slightly", but I would argue that slightly bipolar would refer to someone who has extreme ups and downs but at a lower frequency. Not just someone who gets a little sad and a little happy.

No.

Yes except for ones that are more than slightly, much more than slightly, much much more than slightly, much much much more than slightly, and the dreaded much much much much more than slightly bipolar.

earth is bipolar

I think I'm Tri-polar....I try the ups, I try the downs....somewhere in the middle seems ....o.k., but...Ya gotta try...