It is fucking obnoxious to see people writing with excessive exclamation marks and smiley faces everywhere. Why can't they learn to write properly? If they knew better words they would be able to express themselves without making my eyes sore.
Just in case you don't know me very well, I'll let you know that the above paragraph was bullshit. Anybody who thinks that language shouldn't change or that the way things are is inferior to the way things were should jump off a bridge so that they no longer have to bear the future anymore.
You need to put flourishes in your writing, whether they be visual ones or stylistic. You need to have a style, a feeling. People should be able to read enough of your writing and know that it sounds like you. And the very reason you need to use those flourishes is to gain the power you have by taking those flourishes away.
If your friend is constantly blathering on about random crap, you start tuning it out, but you also expect it. When that friend starts talking in short, direct sentences, you know something is up. They may be angry, sad, hurt, scared. Whatever the cause, the sheer power if undeniable.
This is true both for your own narrative voice and for your characters' voices. An identifiable speech pattern and vocabulary can be powerful by its own right. A strong character giving an impassioned speech can stand all on its own. But to show a change in that character, break that pattern and everybody will know it.