We sellers get all sorts of sob stories about how poor or sick or handicapped or .. or... or... the bidder is. We are very cynical about it. We also tell sellers not to add sob stories to their descriptions , since the usual reaction is "scammer, move on".
I don't understand how a seller could Block you from bidding on one item, but still allow you to bid on others. Or had you bid with him before and were blocked on your last attempt to bid.
I don't like or use Best Offer myself, but from the Boards it seems that those sellers who do will rarely accept offers that are not at least 85% of the asking price.
20% of the asking price is insulting.