I do not know about the long term implications, but what I do know is that regardless I would be contacting Apple about this issue if it were present on my machine. I think that they will want pictures, and will likely want to look at the case to determine what exactly went wrong theirselves.Bump here,
the exact same markings in the same area have shown up on my late 2016 mbp 13" (non touchbar).
it definitely appears to be becoming from under the casing. Seemed to show up randomly.
Curious if anyone has an idea about the cause, or more importantly the long term implications on the overall
case structure / machine.
Thanks