It was a cool feature. It encouraged people to ignore trolls in order to take part in watching their ignore button darken. Maybe prevented some forum drama.
It sounds like a pretty simple yet effective system, it would be nice if Theymos could implement a resource friendly version.
The price of free speech comes at the cost of seeing words you don't agree with. There is no way around it. The good news is no one ties you down and forces you to read anything.
Of course I agree with you on principle. I just thought it would be nice to have something traceable to help those too dense to acknowledge the obvious.