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: Ed's office is located directly behind the right-hand side of the bridge (ie. the side of Kelly's chair, and Bortus and Talla's stations). Ed's office has a prominent window as well. Yet during the closeup flyby of the bridge in this episode at about 55 minutes, the camera pans past the outer hull of that section and there are no visible windows. At that close range we should be seeing directly into Ed's office. Perhaps the digital model makers forgot there should have been a window there.
Continuity mistake: Throughout the episode Bortus and Kelly's uniforms change colour between blue and black and random points, most noticeable in the courtroom scene. (00:54:30)
Continuity mistake: The Xelayan in episode one has no eyebrows, and her nose marks are between her eyes. In episode 2 she has eyebrows and her nose marks are on the bridge of her nose.
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