Continuity mistake: Bortus bites off a big chunk of a drinking glass on a dare, but when he and the crew leave the dining table, the drinking glass is intact.
Continuity mistake: After Bortus bites into the cactus plant, he puts it down on the table twice.
Continuity mistake: When Bortus knocks Kitan into the turnbuckle, her arms slip to the 2nd rope. But in the next shot of her, her arms are now on the top rope.
Continuity mistake: In the opening, Alara takes a bite with her fork held correctly. When the camera shifts to look at the others, it's upside down as she puts it down.
Continuity mistake: Malloy's hand instantly goes from pointing at Captain Mercer to open in the next quick shot while they are in the Krill chapel.
Answer: The book "Flatland", which is mentioned in the show, is a real book that may answer your questions in full (it's the story of a 3-D being experiencing the 2-D world and the 1-D world). In the 2-D world, there is no height, so there's no way to slice anything in half (horizontally). A being living in the 2-D world sees any object or being as a line (it's messy, but the lines have thickness, just not height, but all thickness is the same). So if the Orville was seen, it would only be seen 2 dimensionally and be seen as a line and others beings could just move out of the way. While there were buildings in "Flatland", perhaps this world doesn't have any, or the Orville didn't bump into any. There is death in "Flatland" when a being isn't careful and is poked, but these are usually by lines and triangles and the Orville would more like the circles and not in danger of poking anything.
Bishop73