All what I read is correct so far.

a 3D mesh is defined by vertex, edges and polygons.
But neither of those has a size nor  a thickness. They are indefinetly small and thin.

The "points" and "lines" are visualised depending on screen resolution, but actually, they "have" no size at all.

The only issue is with the numbers. Most sensitive thing is symmetry, weld and mirror.

How "large" an area to considder that the opposite vertex is either symmetrical or not?
Or how "close" is the next vertex to be seen as a "double".

Also the "distance" for automatic welding, for the knife tool.

Most issues I have had are when cicking on Edit => Mesh => Symmetry

Sometimes it moves vertex that should not be moved. (or the other way around)

Have a nice day all.

Poser 1, 2, 3, 4, 5, 7, P8 and PPro2010, P9 and PP2012, P10 and PP2014 Game Dev
"Do not drive faster then your angel can fly"!