I want to mention that replying in Japanese is ok


I will post an ad about an item for sale. I mention everything about the item
in English, but at the end of the ad I want to say, "It's ok to reply in
Japanese."

Is it proper grammar to say "返信は日本語でも大丈夫です!" if an ad is posted online and you
are referring to people responding to the ad?




**ご返信** は日本語でも大丈夫です！ sounds much better. However, 返信 means an answer to spoken
or written communication. It is not used to "answer an ad" (that would be
応募する). お問合せ (enquiry, question) is a better call here: お問い合わせは日本語でも大丈夫です!

