I have a vague recollection from times ancient that when you click "ignore" on a character, it ignores all the messages from that character except orders? Or was that from the time when sending orders were limited to only certain positions?
Also, I do not suppose it would be possible to ignore only certain type of messages such as letters, but let roleplays be visible? The feature, I suppose, is not specifically about ignoring a player (which I do not seek to do) but rather a character instructing his scribes to throw to fire all the letters of another character. I could of course still choose to receive them and only play my character so that he has not in fact received them. But then my OOC knowledge might spill into IC interaction, and I do not want that.
If orders are ignored as well, then I do not think I can use the feature as I would like to.