There is in fact a fairly old (1970s) linguistics theory on this subject. See e.g. Brown & Levinson on politeness theory. You can build some fairly easy softw

There is in fact a fairly old (1970s) linguistics theory on this subject. See e.g. Brown & Levinson on politeness theory. You can build some fairly easy software that applies this on conversational data (1:1 emails, chats, phone transcripts, etc), and it works pretty well.