First of all, let's see if writing typos conforms to the law of Chinese character writing. From the perspective of Chinese characters, typos refer to Chinese characters that do not conform to the standard. Just as in Chinese teaching, calligraphy should also abide by the correct rules of writing Chinese characters. Calligraphers should study hard and master correct Chinese writing skills, and follow these rules in their creation. So from this perspective, calligraphy should not have typos.
However, in the art of calligraphy, artistry and expressiveness are also very important. Sometimes, the use of some typos can bring unique artistic effects to the works. For example, in some calligraphy works, calligraphers will deliberately use some ancient China characters or typos in some ancient cultural allusions to show the quaint traditional flavor. This usage is usually intentional, not because the calligrapher himself is inexperienced, nor because of negligence. In this case, the calligrapher's typo was intentional, not unintentional.
Therefore, whether typos are allowed in calligraphy depends on the specific situation. If the typo is caused by the calligrapher's own technical deficiency or negligence, it should be avoided as much as possible. However, if calligraphers deliberately use some typos in order to express some artistic effect, it is a creative expression and acceptable.
In a word, calligraphy is an art, which should not only abide by the correct rules of writing Chinese characters, but also make innovations and attempts in artistry and expressiveness. Whether typos are allowed in calligraphy creation depends on the specific situation and the purpose of creation.