Most users on Stack Overflow use nongendered pseudonyms, and as a Q&A site, they go out of their way to explicitly discourage conversation. If you do need to a

Most users on Stack Overflow use nongendered pseudonyms, and as a Q&A site, they go out of their way to explicitly discourage conversation. If you do need to a reply to a user in the comments, the convention is @username, no pronouns needed.