@harukan @Burn @ryo It is possible but you convincingly make plausible errors a native Japanese speaker would in English.
You need a good grasp of Japanese and English to fake this and even then it can be a lot of effort.

Lots of Japanese people are on the fediverse and it is plausible one or two would join an English speaking instance because they want to practice.

So it is easier to believe you aren't lying unless we find proof you are.