I can’t figure out the English to mandarin feature for comments.

Under the comment should be a translate button but mine had spontaneously appeared and disappeared

If you are talking about translating something you want to post from English to Chinese, from my understanding there is not a way for you to manually do it in the app other than to copy/paste from a translation app.

That said, I think I heard that Huawei phones, which most Chinese people have, have a built in translation service so typing in English is usually not a problem for comprehension.

I personally still use my iphone’s “Translate” app anyways, but that is just personal preference for me

The translate feature is meant for you to write in your language, and the reader hits the translate button for their language. You don't need to copy in translated ext bc the app is doing that step for you now based on others language settings.

On the left side of the "Reply" button in the comments, there is a translation button, which is about the same size as the "Reply" button. The translation feature is available if you update to the latest version. It works similarly to the translation function under YouTube comments.

If you still don't know how to do it, you can tell me your account, and I'll follow you. I can send you a screenshot from the mobile app through a private message to show you the exact location.

There is a translation button below the comment, but it is only available in the APP version, not on the web version.

I'm pretty sure it's built into the phones, they select the text message and there's a translate button (like in iPhones) the update made it so XHS allows the button to work and made the text compatible