Hi @blackempror first, thank you for introducing your friend to steemit. As in this case, I think you still on the wrong side as you help your friend to post on steemit by commenting using their account. You should have help and guide them; not literally doing what they supposed to do/doing the help yourself.
You see this will bring bad consequences as now you're in as steem community will think that you have a double account.

Hope you can change your approach in helping newcomers/your friend in starting their journey on steemit next time. 🙂