Vietnamese last word bug (duplicated letters)

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Account name

kyrie_g

Account config

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Current Behavior

the site happen trouble handling Vietnamese words that have diacritics (ă, ặ, è, ẹ, ớ, etc.)
at first some word won't even get input.
// EXAMPLE: "đường" (the site will likely don't even record "d" at the start and every letters after that, I need to backspace sometimes for the site to input it)

the final word will always got duplicated with diacritics character
// EXAMPLE: cửa (after typed it all out it will showed as "cưửa" deleting and rewrite doesn't help)

Expected Behavior

base on those 2 examples I provided:
// EXAMPLE: "đường"
-> the site should input and show typed letters like normal

the final word will always got duplicated with diacritics character
// EXAMPLE: cửa
-> the site shouldn't duplicate letters with diacritics

Steps To Reproduce

1. use "words" or "time" mode.
2. type like normal (the 2 problems listed above will likely occur from here)

Environment

• OS: EndeavourOS
• Browser: Zen Browser (flatpak version)
• Browser Version: v1.19.5b

Anything else?

I did tried typing Vietnamese long before this update and none of those problem exist aside from the site flagged diacritics as "wrong" or "incorrect", I do want the devs to talk with someone who actually know how Vietnamese work especially the one who's using Telex type.

I also fcitx5 - unikey for Vietnamese

I'm happy to collaborate and answer more questions if it help the devs improve Vietnamese experience on this wonderful site!

Reproduce the issue in Words or Time mode using the vietnamese_5k language, Zen Browser, and fcitx5-unikey as described. Compare typing and final-word behavior for “đường” and “cửa”; done means Vietnamese diacritics are accepted normally without missed initial input or duplicated final characters.