Is it appropriate for calligraphers to write letters?

Not appropriate. When copying calligraphy works, it is only necessary to sign the copied works normally, and it is not appropriate for the calligrapher to write them on his behalf. Inscription is the written content in calligraphy works except the written content, including the source of the written content, the gift object, the creation reason, the creation time, the author's name, the font size and so on.