An innocuous yet very annoying bug is affecting some users who have updated to iOS 11.1, which. It happens when typing the letter "i." Instead of auto-correcting to a capital, it's instead replaced with the letter "A" and a unicode symbol.
This bug is persistent throughout several different apps but, oddly, not everyone using iOS 11.1 is affected. For those who are, Apple has provided a temporary workaround until a software patch can be issued.
The workaround makes use of the Text Replacement feature built into iOS. You need to create a text replacement that automatically changes a lone lowercase "i" to a capital, effectively overriding the bug.
To create a new text replacement, go to Settings > General > Keyboard > Text Replacement. Next, click on the plus sign in the top right corner. Beside Phrase, type "I," and beside Shortcut, type "i." Tap Save in the top right.
Now when you type "i" and hit space, it should automatically correct itself to "I."