I have not seen an option so replying to a thread seems to be the only way that I can tell.

  • When you click on a user name (at least in the web version), you land on that user’s profile and there’s a button “Send message” to write privately.

    Please note however that the admins of the instances will have access to theses messages, they are not encrypted.

    • yup one of those mental blindness things I think. Even after you said I could not find it and then did a control f and low and behold its like right there. don’t know how I did not see it. even has a mail icon.

      • Do note that you can’t currently message users on other instances from kbin. The button will still be there, but it will bring you back to the homepage. I believe Ernest said something about it being “unimplemented,” so I’m assuming cross-instance messaging will happen someday, but is probably not a high priority at the moment.