The rules are very complicated and they differ from culture to culture and even within cultures. In general, the more detectable the lie the less likely it is to be acceptable. Thus, for example the "How is your day?" replies are socially acceptable in part because it would be extremely difficult to determine that your claim was false. This particular example also isn't the greatest because that inquiry and the standard weakly positive response isn't actually intending for many people to convey meaning. It simply is a pro-forma descriptor that happens to closely resemble a genuine inquiry. This example is actually specific to certain parts of the Western world, and I've met at least one person who upon moving to the US was actually confused until she realized that this greeting was intended in a completely pro-forma fashion (she initially took it as evidence that Americans were very friendly until it was explained to her).

Since the internet has extensive, easily accessible records, lies on the internet about things on the internet are considered particularly unacceptable.

Given Clippy priorities it may be easier to simply wipe humanity out and convert the planet quickly to paperclips rather than trying to use the intensive resources it takes to understand it. Edit: Or at least not spend a lot a resources on trying to understand humans.