The original counter strike supported this. I was certainly guilty of using pornographic sprays back in college in the early 2000s.
The method was explained in detail and concerned the source engine for this exploit. When I search the web for it, I only find articles of the game being banned in China, this feature being removed and then coming back as a monetized feature.
Also searching for this felt extremely sparse.
Maybe you are right and this never happened and it is just some clever internet hoax. The insta ban thing seems far fetched.
But I am certain this was used to troll, protest and circumvent censorship with gusto and must have had some consequences.