It's accepted that we are, by consensus, because of what we experience individually. We know that scientific proof is lacking, although perhaps scientists in the field may disagree, I don't know for sure.
The only reasonable solution is to assume that anything that passes a true, well executed Turing test is conscious
As far as writing messages alone, that could be software.
Like so many fixed things in life, "consciousness" seems to be a frontier, not a demarcation.
For instance, if you're having a lucid dream, are you conscious or unconscious?