I assassinated my cocky counterpart in LD while muffling their screams with a grape jelly and shitake mushroom sandwich, and then relished this dispute by crafting Orichalcum armor in Terraria.

^ several words there that, when modified, could theoretically be violating the filter.

But in reality, the words you're mentioning as examples carry different connotations than what's actually filtered. The less serious ones (or ones that are commonly used in other words) are more specifically defined by the way they're filtered. The Wikipage gives a pretty good idea of how this works.

For example, the word "assassinate" doesn't get filtered because the way it's coded into the game allows for the filter to catch the actual word in context while allowing something like "assassinate" through. It's hard to explain without actually breaking the rules so yeah.

I still wonder why I get to say crap but not a synonym beginning with S.

Possibly because far too many ignorant children use the word as a substitute for that triggering word, to the point OOO saw it as a way of avoiding the chat filter instead of being a delicious fruit.