Then you should know better.
Sore subject I know but what if that person or someone reading it was dying?
Maybe they were posting a load of bollocks because they were seriously ill or clinically depressed and they read you saying "Fuck Off and die" (as a Joke).
When other people read you type that it makes an impression (possibly 100% false).
If that worries you try something else, if it doesn't this thread is not much different than this.