Sometimes, auto-correct may change your text:
1) when typing a date using slashes, it's turned into a fraction, like this: 1/2 > Β½.
2) when adding words after a colon, it's turned into an emoji: :p > π.
3) when putting asterisks before and after a word, the asterisks disappear and the word becomes bold or italicized.
This is happening because, behind the scenes, we have introduced something called a markdown language. Markdown is for people who use these shortcuts to write fast.
There is no way to turn it off, but you can override it by pressing the Backspace key: