* The Scunthorpe problem, AOL didn't let users set their hometown to Scunthorpe because of the "cunt" substring. This is a classic.
* Amazon banning sales of Guns N' Roses merch (because guns).
* People named Miranda having issues with bank transfers (because of the substring "Iran").
* Some games displaying the nickname "Nasser" as "N*er", suggesting that it is the n word.
Alexa not being able to say "pussycat" properly, which is an issue to this day.
* Parental control software that filtered on "anal" in URLs, which also affected "analysis".
* Another parental control software that removed any file with "sex" in the name. This also included "sysext". I know of a school whose entire computer room got bricked because of that bug, the IT person decided it would be a good idea to update all the computers to Windows 10 at once, without checking for software incompatibilities first.
* The British politician Dominic Cummings not being able to set up a Twitter account.