15thc perception on swallowtail merlons?

[Pierre Dumont Himself]

You misunderstood me. I've only called them Guelph merlons because it's easier to type than "regular merlons." I do not think anyone considered them marked in any way or related to the "Guelph" faction until the 19th century. 
As for the battle, the many of the paintings on Wikipedia show swallowtail merlons when there were none, which means there is a chance the painter who drew them correctly knew what they actually looked like. But that's irrelevant. The more important point is that all those other painters should have got it right unless it did not actually matter to them. Perhaps they just thought the swallowtail merlons looked cool. What I tried to illustrate to Stolfi is just what you said: that they almost certainly did not assign the merlons a political meaning when even painters from the same location depicted them in such a coin-toss way.