Clicking with mouse in text field always puts cursor on the end

On both the old and new UI schemes, clicking on a text input field to adjust the cursor does not work. Instead, the cursor jumps to the end of the text as if you pressed the "End" key.

How to reproduce

1. Open chat
2. Type something
3. Try to click earlier in your message to edit there
   → It doesn't work
4. Now use the arrow keys to manually move the cursor one character at a time
5. Now click somewhere again
   → The cursor moved to the end of the text instead of where you clicked