I'll weigh in with a comment from the damp Pacific Northwest of the USA. Every single picture in your post could have been taken somewhere nearby our home. Moss is a battle we fight even in the "dry" summer months.
If I am trying to create a tree that is an imitation of one of these trees outside my door, moss should be a part of the presentation. If I'm trying to create a tree that normally grows in the dry Sierra Nevada mountains, I should consider how unlikely it is for moss to grow on that tree.
Finally, if moss on a tree trunk is truly unhealthy for my tree, do I want to stress out my tree by allowing the moss?
Moss on a tree is as natural as a jin or a burl. Why it is required to be removed makes no sense? We strive to make these little gems as true to nature as possible, moss is part of old growth in most parts of the World. I think it should be displayed.
Living in west Wales, rich fine moss is very indicative of where I live and hence where I collect raw material. So I vote yes to subtle inclusion of moss on a tree trunk, within limits. It alludes to where I live and create my bonsai and displays.
Because bonsai is an illusionary art form, meant to give the impression of something in nature, rather than to represent the actual "real thing", I believe he moss should be removed if the tree is to be exhibited. The tree without the moss is a common denominator that all bonsai artists can understand and appreciate. I have no scientific evidence of this, but it "has been written" that moss on the tree is not beneficial to the tree, and may be harmful by harboring pests and moisture. Obviously, Tony, it is natural in your area of residence as it is in many places in the U.S.
Si lo que se pretende es expresar un arbol que habita en un lugar umbrio, humedo, antiguo, creo que es la mejor manera de que nos transporte a estas zonas.
If what is intended is to express a tree that lives in a shady place, wet, old, I think it is the best way to transport us to these areas.
Mos on a trunk is natural.