Artists do not post their own works on this site, and it is unlikely that they will see your comments here. Danbooru is not like Pixiv or Deviant Art, where artists upload their own works. Users submit the works of artists they like for approval. In fact, self uploading is explicitly discouraged, both in the ToS and the uploading guidelines. If you actually want your comments to be seen and heard by the original artist, it is best to comment by following the source link and posting at the source.