There's multiple issues with text selection specifically.

If you write 2 characters, go to the beginning of the text and then press SHIFT + Right Arrow, it will somehow select 2 characters instead of just a single one.
If you do select everything with CTRL + A and then copy/cut it, the last character will be missing when you paste it.
You can also quickly crash the game when you type a single letter, select it with SHIFT + Left Arrow then CTRL + X it.

I need to rewrite it. It sucks.