My personal preferences:
1) Only use 'well played' when i sincerely feel the opponent overplayed me. So, almost only when i'm about to concede.
2) never use 'well played' when I'm about to win, especially if the match has been very favourable for me.
3) Don´t usually threaten but I don´t feel really threatened or disgusted when my opponent does. It's kinda funny.
4) Don´t like spam. In this case, I silence him/her inmediately.
My 5 cents.
Greetings, traveler. That is only 4 cents worth. Mistakes were made. Your soul shall suffer!