WRITING IN UPPER CASE
it really depends on what you are talking about when you use upper case letters.
In my opinion, writing in upper case CAN be used for emphasis, but these days is so vastly overused that it has become annoying to many of us.
It is also commonly accepted as equivalent to shouting in text speak or instant messaging. When used on the odd word for emphasis, that's fine but when it's the whole sentence, then it becomes irritating.