Yeah I remember being a junior and feeling like blunt comments were kind of rude. So I make an effort to be nicer to new developers - sometimes simply adding “what do you think?”/“do you agree?” is enough to make those command style sentences sound much less blunt, and also encourages them to ask questions instead of blindly following my suggestion if they don’t fully understand it.

The best way I've found to introduce junior developers to code reviews is to pair on it. Just go side-by-side down the diff and hop into an editor when necessary. It also helps teach a developer how to review code and what to look for--which has knock-on benefits of its own.