There appears to be some uneven application of the filter. I've seen some previously replaced words used without being replaced, but when I use them they're still filtered.
I don't know how the forum software works here, but with the stuff I'm used to the Admin has pretty granular control over how different features and settings are applied. It allowed you to adjust individual member's capabilities and privileges based on whatever criteria made sense to you and/or your ruleset. Perhaps that's what we're seeing.