I think no one exactly knows how a shield counter works.

But it maybe related to this.
Shield domes have the tendency to destroy large ships during the last round. It may be a few BS, BC, Destroyers or RIP.
I'm really not not sure if it is the shield dome that destroys the ship. (someone said the battles are computed as a whole and the rounds are just for show)
But in my experience, destroying the shield domes with an IPM usually helps.

I read from one of Mintaka's posts that it has to do with over kill and the extra damage from an attack is redirected at your own ships.

I thought that was the_templar or gumpy. I can't find the thread.

I believe it was on a post about another type of shield.

Zorg has also confirmed that here is a certain amount of feedback from an attack (especially from overkill) that will result in some strange results. They're working at resolving the issue.

neoshagrath wrote:I thought that was the_templar or gumpy. I can't find the thread.

It was gumpy

Sorry for my mistake and sorry Gummpy.

from my experience, I've only had my larger ships taken out by shield counter if i didn't overkill enough. (as in demolish in first round)