[Aardvark]

My question is, do you get banned if nobody reports you? As in are there telltale signs that I am doing things like teleporting if I am around nobody, teleporting 5 feet upwards max, or gathering in an area with nobody around?

In some cases, yes, if they are monitoring server-side data that proves you cheated.

An example would be if you use teleporting to gather all the aether currents in an impossibly little amount of time, you'll typically get suspended on a 2nd or 3rd Wednesday.

My accounts that teleport sparingly in public spaces, or as much as I want in personal instances, are consistently OK.  (Just my experience, your mileage may vary.)  For that reason I can definitely say that teleporting isn't "detected", but what teleporting allows you to accomplish might be exposed through their server-side telemetry.