Reproduction steps (Original):
1. Open the attached “IN-102260_LIVE-unity-test.zip“ project
2. Open the “Assets/Scenes/CityMap.Unity“ Scene
3. Using “WASD” walk next to the NPC in the bottom right
4. Open the chat in the game by pressing “Space” near the highlighted character
5. Using the Mac IME, type any Japanese text in the text field, without sending it/hitting Enter.
6. Attempt to delete text in the field using the delete/backspace key

Expected result: Each character is deleted one by one
Actual result: Characters don't delete right away, delete in chunks, or the text field becomes "stuck"

Reproducible with: 1.9.0 (6000.1.16f1), 1.14.2 (6000.0.50f1, 6000.1.6f1, 6000.2.0b4)
Couldn’t test with: 2022.3.63f1 (Unable to downgrade)

Reproducible on: M1 Max MacOS 15.1.1
Not reproducible on: No other environment tested

Note: If the chat gets “stuck“, closing and reopening the chat shows the text from the previous session when trying to type, even though closing the chat should clear the text field

Note: I was able to reproduce with a simple UI Toolkit textfield in an empty scene. I've also added a clip showcasing how the backsapce events are not sent when IME is in use which seems to be the root cause of the issue.