doesn't proffer carry a sense of 'social diffidence'

I would agree with that, and, further, I believe"proffer" carries a connotation of direct transaction with a specified person or group. You can make an offer to the world in general - especially a "Special Offer - ends next Millennium - hurry and buy" - whereas you "proffer" something to someone in particular - "On behalf of the Misused Word Club, I would like to proffer our thanks to this evening's squeaker, Mrs Malaprop, for an entertaining and enlightening evening."