Censorship

So I was chatting to my friend and as it turns out "D7" is censored when i type it into chat. I'm not sure if its a bug or if i just don't understand what D7 means if its so bad it has to be censored. For some reason my friend doesnt see D7 as censored so i was just wondering if this was something on my end or just a bug.

https://gyazo.com/45ebe7e620cf3d57209ed43e94e3080d <--------- what i see

https://gyazo.com/572dfbb0d7c5ec1f3c9d008b77555a48 <------ what my friend sees