1.) Negatives for all sellers/buyers of accounts is potentially not effective for targetting account farmers:
That is not a negative, that is a positive. You should not be selling accounts in the first place.
Not if it increases profits of hardcore account farmers due to them being the only people who sell accounts in the short term. Negatives mean nothing on some random newbie account.
Also in longer term you strengthen anonymous account farmers position and alienate hundreds of better quality members in 1 swoop.