Unfortunately, at least one Advy player (the one who I noticed this with) has said his character has been attacked by nobles for "impersonating a noble" because of the Sir tag.
I agree completely that they should have something to signify that they're donors, but that Sir is inappropriate for an adventurer. As to what... That's one of the reasons I put this here, so that it can be discussed some. I'll confess I don't exactly know what sort of titles, if any, would have been appropriate for Freemen.
