I don't think this would be a good default behavior, since the significance of a much repeated error might depend upon the errors imediatly before and after it. However, a checkbox in the JS console to turn this on would be a good idea. Confirming as NEW, changing Platform/OS to "All/All".
Perhaps the right thing to do here is exponential backoff (possibly in the console service itself)? That is keep track of errors we've seen. If we get one just like one we already got, and we've gotten it a lot recently (the exact definitions of "a lot" and "recently" are up for debate") we ignore it. This way as long as an error is repeating we will report it, but say no more often than once a second (or whatever "recently" is), though in the first second of reporting, for example, it we would report it as many times as it happens. Thoughts? We really do want something like this on by default if we're going to turn on CSS error reporting in release builds....
*** Bug 206874 has been marked as a duplicate of this bug. ***
Is this bug a dublicate of bug 80704 - both are about removing dublicate entries in JS console