ISSUE:About a professor told us don’t use too many “Mar language” in examination or formal letter

Today a professor told us don’t use too many “Mar language” in examination or formal letter.
“Mar language” is a phenomenon, incompletely understood at best, in which young people develops a unique language with highly original marks in computer keyboards. Many people uses them due to they can save time of typing while talking with friends on internet. Meanwhile, many marks are looks interesting. Therefore, it is hard to prevent young people from using them in handwriting, I think.