Wireframe view in object mode - which lines are drawn?

Until now I thought, that wireframe view in object mode draws the outlines/outer edges of every object but no edges, that lie within a plane. In short: It draws only when geometrical changes have to be visualised.

Today I modelled a plane and subdivided it. I then deleted a couple of faces and inserted circles and then connected all vertices back to faces. Everything still lies on the same plane. (I checked that by selecting all vertices and aligning them to the cursor in one axis.)

When I enter object mode and wireframe some of the circles and some connecting edges within the plane are drawn, but not all of them. Can anyone explain to me if there is any rule behind this?

(I actually wanted to use the wireframe in object mode to see if my plane is still perfectly flat, which I thought would result in nothing in between the 4 outer edges. So now I keep on thinking that something is wrong with my mesh, but I couldn’t spot any mistake. No double faces or anything.)

Planar edges are not drawn most of the time. Occasionally, whatever algorithm calculates this gets it wrong as outlines a planar shape. I have never been able to get a good answer for why. Go into the ‘N’ panel and under display click ‘Display All Edges’ if you’d like to see everything, but I wouldn’t rely on it to measure how planar your edges are.

Ok, I’ll be aware of that in the future. Thanks.