Ah yes, that is true. You have to also mention the user in the text. So if you reply to a tweet from “@test” and you want to post the reply “hello” you would have to post “@test hello”.
I just checked the Twitter API and saw that they have an option to do that automatically. I activated this option now. It will be released with the next version and so that will then not be needed anymore.
One other important thing to mention. If you get the ID for the Reply from Twitter you have to use “id_str” and not “id”.