[levi_n]

My favorite is Fark's word-changing filters and their unintended side effects. The no-no words are scanned across whitespace and reversed, and any hits get translated to the approved word. "Shit" becomes "Shiat", the N word becomes "nubian", etc

Every so often someone will find their sentence that contains something like "I will have ham or egg in my sandwich" becomes "I will have ham onaibun my sandwich"

[iggldiggl]

Reminds me of Yahoo's botched e-mail filter in the early 2000s, when in an attempt to prevent Javascript exploits they automatically replaced all occurrences of a few script-related keywords with alternative terms – even in the text body of a mail and without regards to word boundaries. "eval" got replaced by "review", leading to such words as "medireview" (medieval), "reviewuation" (evaluation), "rereviewuation" (reevaluation), "prreviewent" (prevalent) and suchlike.

If you search for some of those terms, you can still find traces of them across the internet and even in some published scientific papers.