Typing and de-emoji-ifying some emoji in a post prevents typing on the same line after the emoji

[ZMYaro]

To reproduce:

1. Open the composer (for a new post or a reply).
2. Insert a ™ or ☑️ character from the symbols panel.
3. Press Backspace once to de-emoji-ify it.
4. Attempt to type on the same line after the character.

Expected result: You should be able to keep typing.

Actual result: Every keystroke inserts a new emoji-ified version of the character.

Browsers tested: Chrome 110 stable and Firefox 110 stable on Windows 11

Video of the issue: tm_char_bug.webm

Additional notes: This happens with some emoji, but not all. Backspace turns them all from twemoji to system font emoji, but not all start inserting duplicates. From a bit of poking, it seems as though a lot of symbol emoji have the duplication issue, and a lot of face emoji do not.

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[daisylb]

I'm also experiencing this; I have a macOS Text Replacement that turns ,tm into ™, and it results in the same behaviour:

Screen Recording 2023-03-06 at 16.15.38.webm

I'm using Safari Version 16.1 (18614.2.9.1.12), if it helps.

[daisylb]

I haven't exhaustively verified this, but it seems that this only affects emoji that are represented by characters that default to the text presentation, and which end in U+FE0F VARIATION SELECTOR-16 to turn them into the emoji presentation.

Other things I've noticed:

• The behaviour of backspacing to "un-emojify" the character only happens when the bug is triggered. (I'm guessing backspacing is removing the U+FE0F, which is causing this problem somehow, but that's a guess.) In all other circumstances, backspacing removes the entire emoji sequence.
• The bug is only triggered if you press backspace immediately after typing the character. If you type anything else, anywhere else, and then go back to the character to try to backspace it, the bug isn't triggered. Focusing away from the text field and then back again doesn't stop the bug from being triggered.
• The bug affects all text inserted after (e.g. "to the right" in a LTR context) the character that triggers it, either on the same or following lines; text can still be entered prior to the triggering character as normal.