I don't think deer are that smart to see a fence/flag or wire , to mean safety zone
BUT what they will learn is, that certain area's places are safer than others.
its just nature at work
the only reason to add wire or markings IMO< would be for humans to follow
animals will find out on there own what is a safe place and what isn't and use there natural skills to do so!

might be over thinking things here IMO

but like any hunting tool, if doing somethings gives you confidence, have at it,!