I would like to see the ebay rule that says you can't tell the reserve.
I always ask if I am interested in bidding on an item. If the seller won't tell then I won't bid.
The reason the bidder needs to know is so they can decide if it is worth waiting or bidding on one from another seller. For example, there is an item with reserve ending in 3 days that is at $100. There is another item at $200 ending in 2 days. If the item with the reserve had a $150 reserve then I would bid on it. If it had a $250 reserve then I would only bid up to $250 on the first item. If I don't know the reserve then I would just buy the first item (assuming it went in my price range) I can't bid $200 on the item with the reserve right away because if I meet the reserve then I can't bid on the item ending sooner. If no one else bids, there would be no problem but there is a good chance the earlier auction will end at the $200 bid and then I get outbid on the item that had the reserve. Now I have to start all over looking for a new item.