Is it actually a useful option in your opinion? To me, the cost doesn't seem to make it worth it.
On an individual level, I find some use but it's definitely marginal. It can have a big effect on your image to have that little push that makes your unit appear to be 1'000 CS, especially if you're the only one in an army/realm to achieve that. It can also make that overzealous marshal or general who insists on controlling everyone's unit get off your back.
As a diplomat, you can use the inverse effect to make a sizable unit look weak and inconsequential when visiting realms who get nervous seeing big units approching.
As a tactical maneuver on an army level, I've never used it; I don't think it would extremely useful, but for all I know I just haven't figured out how to use it correctly.
