The reason C grids are used for sharp trailing edges is that the (i,j) corner of an O being at the trailing edge creates problems at the slip surface of the trailing edge due to the need to overlap in both directions there around a sharp corner. You basically have to bend the mesh around a 180 turn in two cells, which wreaks havoc with the smoothness assumptions of your analysis.

A C mesh doesn’t have that problem, but the overlap of the C can also create some issues when using implicit methods, unless you overlap by two or more cells, depending on the order of the dissipation and method.

An H mesh is similar to a C WRT the trailing edge, but we never used it because of the aforementioned extension of near wing boundary layer cluster on the front of the wing to the boundary - wasted points...