You won’t be able to fix this on Crowdin even after you sign up there. If that were possible, I would have done that based on your report, even though I don’t know Japanese. The text with the additional “h” was approved years ago, and as a community contributor, you can suggest a new translation, but this won’t appear in Discourse without being approved.
When a new text is added to Discourse, you can suggest a translation, which is added into Discourse. Then, you or someone else could suggest a different translation, for example, because you notice that in this context a different translation would be better, or you notice a typo. Discourse will take the latest translation that has been added.
Someday, someone with proofreading permission will take a look at the translation and approve one of the suggestions. After that, you can still suggest a different translation, but you need a proofreader to approve that to achieve a change in Discourse.
Proofreading in Japanese is handled by a translation agency. Usually, they worked on the translations before an extended support release (stable release) was released. This didn’t happen in January. (So, in the case of Japanese, it’s a mix of volunteer translations approved by the translation agency and translations directly done by them.)
I think members of the Discourse team can also handle this, but there is not much we can do. You can add a comment that the translation is wrong, but you still need someone with proofreading permissions to take care of this.
This is something that will happen often. New texts are added almost every day, and as long as no one enters a translation in Crowdin, the text will be shown in English. It also happens that texts are entered in the code, so they cannot be translated, but this is not the case here. This one is available for translation, but no one entered one
If you want to help translate Discourse and struggle with the interface in Crowdin, I am happy to help. I still remember how confusing the interface was for me when I started translating.