You are trivializing my point. I'm not referring to the omission of a comma; and I don't believe the letter in question was simply missing a comma. Although, we were all taught how to correctly place commas in sentences. I'm referring to grammatically incorrect sentences, misspelled words, inappropriate participles, run on sentences.
Sending any communication without benefit of spell check or proofreading shows the sender is not overly concerned with how he presents himself. It also demonstrates that he is little disturbed by the fact that he thinks little enough of the recipient.
How we dress, how we conduct ourselves in public, how we converse, and even how we write are windows. Must a suit be one thousand dollars? No, but it should be neat and tidy. Is is imperative to know which fork to use for the seafood course? If you are planning to dine at a seafood restaurant, it is. Should we endeavour to speak clearly and concisely? Whyever would anyone ever consider otherwise?
Conversely, a letter delivered with errors is of little consequence, at the end of the day. However, it's the decided nature of society that one letter, one conversation, one meal in the presence of a boor is 'no big thing'. It's the adding and continued adding on of more improprieties that disturbs me. I reject that it's okay to have a couple of errors. If I permit it, then I'm demonstrating that I really don't deserve the very best that someone has to offer. If I continue to permit it, than I only serve to add to the situation.