You could say that -- it's possible to make a filter sound like a giant popcorn popper, and to end up with pinholes in your cartridge.

I tend to shy away from describing some of the more 'active' reactions, since as soon as I do someone's going to run out and try it, and possibly hurt themselves or someone else.

Simple rule? Never let any form of chlorine come into direct contact with any OTHER form of chlorine, or any other chemical. There are a few chemicals, like borax, that don't react badly in contact with various forms of chlorine, but it's safer to assume that EVERYTHING reacts badly.