I've experienced both sides of
ebay frustration as buyer and seller, never been blocked but I do know that contacting a seller to sidestep an auction can be frustrating for a seller.
I sold an item that was part of a lot (several items together), I didn't want to separate the items , the item was very rare and sought after, I was contacted by several people with requests of I only need 1 item and I'll pay you $80 for it which I feel is reasonable , another contact offered $200 , after all was said and done and 30 seconds left the sniping began and the bid ended at $360.00 .
As a buyer I've played sniper been sniped and I also have had the same dilemma of not being able to bid at the auctions closing , my suggestion when this happens is to place the highest amount bid that you're willing to spend and leave it to chance , at least the winner will have to outbid you and will not get the item for nothing had you not placed a bid (on below priced auctions).
Don't take being blocked as a personal attack , some sellers go through alot and would rather block you than mediate any type of deal.
......and then there is
ebay who deducts fees from everyone even when transactions go wrong and there is no sale , I've spent hours with customer service getting back a fee just out of priciple.