At the bottom of the game, you have an area to leave messages, by default, if you write there, he will receive a notification.
Although it is public, it is a more specific area.
I'm assuming you've already looked, but many developers put their contact information, such as social networks, in their profile.
PS: If I have misunderstood you, and you are giving feedback on the platform, then it would be best if you wrote in the section ideas-feedback