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Your LimeSurvey version: 6.4.0+
Own server or LimeSurvey hosting: Both
Survey theme/template: Fruity
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Some of the text messages in editing a question, such as "Answer options order" and "Position for 'Other:' option," is only available in English without translations. Translating these messages are impossible currently. Is there a reason for having untranslated UI messages? Thank you in advance.

It's advisable to check for platform updates and check community.limesurvey.org/downloads/

It's advisable to check for platform updates and check

???
You see the issue is that these texts are not included in the translation file.
And they were not included in version 5.x. as well.
Therefore my guess is: They were forgotten.
The best is to file a bug report.

Joffm

I'm wondering if missing original messages in .pot and .po files should be considered a bug.
 

Filing a bug report might be the best course of action to rectify this issue for improved user experience.

"text - correction, missing translation, typo" is a part of issue reporting. Today I know that. Thank you.