I've never used the sunder rules...but if I had an indestructible blade, I'd make a nice, beefy sundering PC...as per my answer.
I don't have my 3.5E books anymore but I don't recall the sunder-er taking damage to his weapon so per that system I'm not sure what difference it makes if you have that weapon or not if you decide to sunder. I supposed it would help with the inevitable ref counter reaction of sundering the PC but then why not carry a backup weapon or two?
But perhaps I mis-remember this part of the rules. As I said, we didn't sunder much.
It was one of those things that seemed unbalancing in the short term and distorting in the long term: build a PC around sundering and the ref will naturally create counter measures: unsunderable weapons or have the foes all have multiple weapons at the ready or sunder the party's weapons more than they desire or simply use more foes with natural weapons. As you say, foreseeable. So why invest in sunder.
So, if you have a weapon that cannot be broken, having a PC who takes advantage of that fact by breaking other things with it is...forseeable.
The fact that it can't be broken doesn't imply that it can itself break everything else or that it becomes the be-all-and-end-all of the campaign. For instance, apply said elephant (per another poster on this thread) to the sword used as a lever on a vault and the elephant is more likely to have the hilt of the sword painfully embedded in its body than the vault opened. Or the fulcruum point give out.
But if your point is more along the lines of this sort of thing has unintended consequences, than I'd certainly agree.
Even so, as I ref were I to put in an indestructible sword and then find it a nuisance I'd let it break at some point. It's not like it came with a warranty backed by the creator of the universe. Someone told the PCs it was undestructable, for a long time it seemed pretty indestructible, but oops, they were wrong. How did the PCs know it was really indestructible? It's hearsay backed up by a certain amount of evidence but maybe it was just mostly indestructible.
Both the game world and the real world are full of exagerrated labels
