It doesn't bother me in the slightest - it honestly feels a bit more polite than just barreling in with a question. I was sort of surprised when I found out just how passionately it bothers the people it does bother, though, so I've made a conscious effort to stop doing it.
I'm 100% fine with Hi. <Press enter> <Ask Question>. It's Hi <Press Enter> <Wait for a response> <Ask Question> that makes me homicidal. It makes it completely impossible for me to prioritize this discussion.
The difference is that when you press enter I get an alert. Then you take 30 seconds or 2 minutes (or more) to think through and type out your question. Now I just have to sit there waiting for your question.