カスタムモデレーションフラグに関連するサイトテキストの変更・追加?

I don’t think the problem is related to a specific translation.

When a post is hidden because of flags from the community a personal message is sent to the author. This message contains a reason. For example:

These reasons are used when the message is created.

The code which adds this reason to the message uses the post_action_type

That works for the default flag reasons. For example, flag_reasons.spam, as seen in the screenshot above.
The problem is that there is no such string for custom flag reasons. For example, if you create a “Testing” reason and enable Auto hide flagged content.

Then flag_reasons.custom_testing is used. However, this reason does not exist. The language doesn’t matter; it does not even exist in English because it’s a custom flag.

And the same reason is also used when the post is deleted (see screenshot in RGJ’s post)

By the way for “responders” the illegal reason is missing too

「いいね!」 4