I symbolize subscripted variables with the form TraditionalForm, to enable easy use of TeXForm as suggested here:
Needs["Notation`"] Symbolize[ParsedBoxWrapper[SubscriptBox["_", "_"]], WorkingForm -> TraditionalForm]
However: note the following example:
rule = f -> ftest; Subscript[f, a] /. rule
The rule replaces the "f" in Subscript[f,a]. This is of course not wanted, as I want to treat f and Subscript[f,a] as different entities. If I do not use the WorkingForm on TraditionalForm, this works as expected, but now for some reason, it has this behaviour???