When it comes to italics, there seem to be two camps. Love them, and hate them. It can sometimes feel like the Marmite of the writing world, and just like marmite, personally, I hate them.
I just can’t stand reading something when every other word is in italics.
Of course, italics do have a place. If something isn’t dialogue, but isn’t part of the normal prose, they are needed to differentiate whatever it is we’re reading. So a sign, or a note, or, in general, something the character is reading. But a letter doesn’t have to be in italics. It can be, of course, but usually if the prose switches to a letter format, we know what it means.
However, my main issue with italics is when they’re used to emphasise. For some reason, something about their use has the potential to completely jerk me out of the story (depending on the quality of writing, anyway). If I’m wrapped up in the plot, I’ll skim over it, otherwise it’ll make me pause.
The best way to explain it is to repeat the words of a tutor at uni, during one Creative Writing seminar. Italics, when used for emphasis, show a lack of trust in the reader. It means the writer doesn’t think they can work out for themselves how the words are spoken (if in dialogue) or read. And they can be jarring. Everyone will read in slightly different ways, and if the way a person reads naturally puts the emphasis on a different word, seeing it in another place in the sentence can jar them out. For whatever reason, an emphasis on word three in a sentence, as opposed to word five, might just not make sense to them.
So, basically, to me, italics for emphasis = underestimating the reader.
And then there are direct thoughts. Something else that can, if not written well, really get under my skin. To me, too often, the character’s ‘thoughts’ don’t read like actual thoughts, and feel too much like over-explaining, too much like telling rather than showing.
It’s having a character think, Oh, I’m so frightened, as opposed to saying goosebumps scattered across their arms, hairs stood on end, they were frozen, their heart thumped, their pulse raced, etc. Or, describing the fear, then having a character think that. Once more, underestimating the reader, not trusting them to understand something they’ve already seen.
So that’s my main ‘issue’ with italics, really. The things they’re used for tend to lean towards the idea that the writer doesn’t trust the reader or, perhaps, they don’t trust their own writing to speak for itself. They have their place, and can be used for good, but should be used sparingly.