Tone when communicating online is important, if the wrong tone is used it relays the wrong feeling. Also, depending on with whom you are communicating, an exclamation point at the end of a sentence can change the mean of a statement all together. Depending on if the person is a friend, family member or just an acquaintance, the conversation can be a little less formal, but I still would say that using correct punctuation and full statements should always be the case. This always or at least for the majority of the time will help eliminate confusion.
When sending official correspondence it is important to write and check what you have written. For myself, I will write something and print it out, read it, check it for errors and edit it, before sending it to the recipient. This will ensure fullness and correctness. It is sad when you send an official letter to someone and they deny you for something they may have misunderstood. It like when you apply for a job or a higher position in a company, if what you have written makes no sense, has a lot of misspelled words or has grammatical errors, it should be no surprise if someone else get the job. I was always taught to write as if I were trying to sell an idea. As when you read a book or and article, if they like do not what they read then you did not apply yourself. Writing is an art and a tool for communication. It should always be treated as such. I learn to better my writing skill by writing my thought down, in a journal. It helps me keep track of my ability to articulate and allows me to see my accuracy in sentence structure....