Deleting emojis sometimes only deletes part of them, leads to weird characters send

[Bubu]

Describe the bug

While trying to find the cause of #3449 I instead found a different issue that I've occasionally seen before:

To Reproduce

Steps to reproduce the behavior:

1. Type :;
2. Select the 😉 emoji from the completer
3. Use backspace once, the emoji will still be there
4. Send message
5. See that a ? message got sent

This was tested on Gboard and SimpleKeyboard (from F-Droid)

Expected behavior

Emoji gets properly deleted on backspace

Smartphone (please complete the following information):

• Device: Pixel 4a
• OS: Android 11

Additional context

• 1.1.8 from Gplay

[SpiritCroc]

I can reproduce this on self-built 1.1.8 Element, F-Droid variant.

Some additional findings: the keyboard in use seems to play a role here, since AnySoftKeyboard and FlorisBoard do not suffice to reproduce the issue, but the AOSP keyboard and SimpleKeyboard do. Furthermore, when making the EditText an AppCompatEditText instead of an EmojiEditText (as done in SchildiChat), you will see before sending that the emoji was not properly deleted.