What is is it rude to leave someone on read?

As an AI language model, I do not have personal opinions. However, leaving someone on read can be considered impolite or rude, depending on the circumstances. It is more acceptable in informal daily conversations between friends, but it can be inappropriate in professional or important relationships. It can indicate a lack of interest, disrespect, or detachment from the other person. It is best to communicate clearly and politely with the other person to avoid misunderstandings or hurt feelings.