As I was performing the 9th oil change, I almost flipped.

There is a <1" area of paint and metal substantially eaten near the battery.

I haven't had cause to add water in >6 mo. (and then it was only drops) and all cells look OK right now, but clearly there's been battery acid doing it's work.
I've never had any charging or starting problems, have never even disconnected the battery, and no caps were loose. I just poured baking soda in the area of the damage, but haven't removed the battery and tray yet. A stain on the floor (actually carpet) in this area (which I assumed was road salt) showed up >1 month before this cold snap - but car is normally in garage anyway.

1) Has this been heard of?
2) I don't think the dealer removed battery to change the headlight harness when the service campaign was performed last summer and battery seems held down ok (enough) - though I assume there's only 1 clip on left side (as I said I've never had cause to remove).
3) Should I take this on myself - as I do almost everything? Thoughts?
4) I can't stand to bring it to the dealer to watch him laugh as he charges me $130 plus 2 hours labor for a battery which I may or may not need (and he won't repair the paint/metal damage) and will likely just shrug his shoulders.
5) Do I have any hopes under the 4 year warantee.....?
Thanks all.

Mark R.
2000 C70 Conv.
25,000 miles
delivered new 12/29/1999