A renter who wants to increase chances of securing the property bids up the rent to reduce "plain old competition"? Um, isn't that just a market? I also understand there are now laws preventing the practice of bidding above an advertised price, at least there are in Victoria along with a myriad of other tenant friendly regulation. However, obviously if there was ample supply of rental accommodation those practices would not happen. In a scenario where the market is oversupplied as a tenant you might be able to offer less than advertised, although I don't think we hear grumblings about that when it happens do we?
Tight supply enables landlords to raise rents to make greater "profits"? Yes, that is called a market Scott and whether a property manager wants higher rents to extract commission is irrelevant because a rental sitting on the market overpriced gets the agent nothing.