Did you know that it is rude to finish your message with a full stop? Apparently this is an indication that the conclusion is a somewhat pointed remark.
And who would have guessed that a smiley face in the wrong context can be taken as a hint of sarcasm? :)
On asking how we are supposed to know these things, it was not very reassuring to be told "it doesn't matter for you because you are old". Hmm . . . not all that old! I don't yet know what I want to do when I grow up!
But apparently I am safe, so if you find me committing either of those offences please forgive my age! I'll continue with my opinion that it is rude not to punctuate your sentences properly.