It seems to me that out hobby is still so new that, as yet, there is little agreement on terminology or even on the principles of what constitutes a desirable vintage bike.
Some attempt to borrow (incorrectly) terminology and therefore ideas, from the fine arts and antiques fields and apply them to vintage bikes.
One of these terms is "patina". Patina is a film formed on bronze or copper by treatment with acids or exposure to the elements over time. By analogy it also refers to a surface mellowing with age or use. To apply this terminology to steel bikes' rust and corrosion is specious and incorrect. In the field of fine arts and antiques, damage, such as by mildew, parasites, "foxing", etc., is not patina-it's simply damage. Rust is damage. In fact, if a rusted bike is left alone, the damage will progress and, eventually, where ferrous metals are involved, only rust will remain. Some collectors would like to make vice into virtue by claiming their rusted and damaged bikes are in a more "natural" state, etc., but, in reality, and for a variety of reasons, they lack the will or means to perform the proper repairs (or have others do them), and would have the world believe that their damaged bikes have "patina". In time, however, they will have nothing.
In my opinion, the repair of each bike should be individualized-severe damage will require drastic means and slight damage only the mildest of remedies. Naturally, the more drastic the repair, the greater the talent needed to effect it, and, in most cases, the greater the cost. Each collector must somehow titrate the value of a damaged bike (which might be subjective in some cases, but not all) against the extent and cost of repair.
George
George Hollenberg MD
CT, USA